OS/2 is designed to run OS/2, DOS, and Windows 3.1 (if the user already owns Windows, or if OS/2 with Win-OS/2 is purchased) programs. For the most part, it does so quite well; however, OS/2 runs some programs better than others, and how well it runs these programs depends to some extent upon the user's hardware and to a large extent upon how well the system is configured.
Obviously, how well OS/2 runs an OS/2 program depends upon how well-written the OS/2 program is. Unfortunately, many OS/2 programs are quick "ports" of a DOS, Windows, or sometimes a Unix program, and these ports sometimes don't run terribly well. One of the worst offenders in this category is the (now-defunct) WordPerfect 5.2 for OS/2, which was a buggy and slow port of WordPerfect 5.2 for Windows. On the bright side, an increasing number of companies and shareware authors are learning how to utilize OS/2's features to produce fast and flexible software. Some examples: DeScribe 5.0 is a reasonably well-designed OS/2 word processor, and the new ClearLook word processor makes even better use of OS/2's features. The shareware ZOC terminal program and KWQ Mail/2 offline mail reader both perform well and utilize many of OS/2's features to good effect. Many OS/2 GIF and JPEG viewers are faster than their DOS and Windows 3.1 counterparts.
DOS applications generally run as well under OS/2 as they do under DOS, and with the added benefit that they can be configured individually and run simultaneously. DOS programs sometimes present difficulties, however, if they are very timing-sensitive (such as terminal programs doing file transfers or tape backup programs) or if they need to access the computer's hardware or disks directly (such as disk defraggers). Some games (and even applications) require a lot of tweaking of the "DOS settings" to run well, and a few don't run at all under OS/2. CPU- intensive DOS programs may take a slight performance hit due to OS/2 stealing CPU cycles from them to perform its own tasks, but this generally isn't very great. As a rule, DOS programs don't multitask as well as OS/2 programs, since DOS programs tend to "busy wait" -- they tie up the CPU simply waiting for a keypress or other system event. Disk-intensive DOS programs may experience a performance hit or a performance gain, depending upon the hard drive setups. HPFS's advantages may give a performance boost for DOS programs that use the disk heavily.
Windows 3.1 programs generally present fewer multitasking problems than do DOS programs. Windows programs are also less likely to want access to low-level hardware that OS/2 wants for its own. Because Windows itself is fairly memory-intensive, however, many Windows programs put enough of a strain on a computer's RAM reserve that they run more slowly under OS/2 than under DOS/Windows. This is especially a problem for users with relatively little RAM (say, 8MB or less) and/or those who installed OS/2's multimedia support and IBM Works, both of which chew up RAM. Some Windows multimedia titles, especially those based upon all but the oldest versions of Apple's QuickTime, may not run properly under OS/2; but other Windows multimedia titles run fine, especially in full-screen mode. The video drivers which OS/2 provides to allow Windows programs to run "seamlessly" (side-by-side with OS/2 programs) necessarily result in a worsening of video performance, since these drivers must interface with OS/2's drivers, and this overhead slows things down. Video performance can usually be improved considerably by running Windows programs "full-screen" -- they take over the video display. These adverse speed effects can be reduced by careful management of OS/2's CONFIG.SYS file and other settings, and many people find that they can run Windows programs as well under OS/2 as under DOS/Windows. Others, however, particularly those with less RAM, become frustrated by OS/2's performance with Windows programs.
In the post-Windows 3.1 era, there are several types of 32-bit Windows applications. Most of these are now marketed as being "for Windows 95" in some sense or another, but most of these are actually what's known as "Win32s" programs -- they use a subset of the Windows 95 features, and will run under Windows 3.1 when it uses the Win32s extender. OS/2 also supports the Win32s extender, and so will run most (but not all) of these titles. Thus, although OS/2 does not run any "real" Windows 95 programs, it does run many of the programs that are marketed for Windows 95. Similarly, a number of recent games are being marketed for Windows 95, but in fact they're DOS games that often run under OS/2. Check the box's system requirements carefully on any such program you're considering. If it lists DOS or Windows 3.1 with Win32s as a minimum system, chances are that OS/2 3.0 or later will run it, though this isn't guaranteed.
Since OS/2 runs Windows in order to use Windows programs, most Windows features, including TrueType fonts, are available to Windows programs under OS/2. TrueType fonts are not available to native OS/2 programs, in OS/2 3.0 or earlier, however. Instead, OS/2 uses ATM fonts (also known as Type 1 or PostScript Type 1 fonts) for OS/2 programs. OS/2 also includes a version of ATM for Windows, so the same PostScript fonts can be used for both OS/2 and Windows. With the release of Merlin, OS/2 will support TrueType fonts in addition to ATM fonts. There are a handful of commercial font conversion programs, such as FontMonger, but there are no freeware or shareware programs for converting TrueType to PostScript fonts. One good source of ATM fonts that can be used with OS/2 is the Bitstream 500 Font CD for Windows, which sells for $20-$40. Another good ATM font collection is the Expert Software 2000 Fantastic Fonts for Windows CD, which costs about $15. Avoid the SoftKey KeyFonts Plus and KeyFonts Pro collections; the former, despite the label, does not include PostScript fonts; and the latter lacks the .AFM files that OS/2 needs (though these can be regenerated with the PFM2AFM program). There are numerous freeware and shareware fonts on Hobbes, as well.
For all three types of software (OS/2, DOS, and Windows), a complete list of software that runs well and software that doesn't is beyond the scope of this FAQ. If you're concerned about a specific program or set of programs, post your question. (Do not e-mail me about this, please; I use few DOS and Windows programs, and so probably don't know the answer to the specific query.) Note that "does it run DOS games?" is too vague; list the specific games that you want to run. (There is a comp.os.os2.games newsgroup for such questions, too.)
Running OS/2 does not preclude running native DOS (with or without Windows), Linux, Windows NT, Windows 95, or any other operating system. OS/2 can coexist on a single FAT boot partition with DOS using a method known as Dual Boot; or OS/2 can be installed on a separate partition and a program (included with OS/2) called Boot Manager can be used to select the boot partition. Dual Boot is easier to install but more limited in its capabilities, while Boot Manager is more difficult to install but more flexible in use. One tip: Installing Boot Manager becomes MUCH easier if you can shrink the size of existing partitions. This can be accomplished with either the commercial utility PartitionMagic (under $100), or with the (much more limited) freeware utility FIPS. There's also a shareware utility called Advanced Boot Manager that allows the installation of multiple OSes on a single C: FAT partition. Although the name of this utility is similar to OS/2's Boot Manager, it's really more like OS/2's Dual Boot in many ways, but more flexible.
Thus, the type of applications you use will influence the answer to the question, "should I buy OS/2?". If you run mostly Windows programs, and have no intention of or desire to switch to OS/2 programs, you should give points to a "no" answer. Ditto if you run exotic games and/or DOS programs that must access low-level hardware. If you're willing to investigate native OS/2 software, however, or if you run multiple DOS or Windows 3.1 programs requiring different DOS CONFIG.SYS or AUTOEXEC.BAT files, OS/2 is worth consideration. OS/2 is also worth a look if you want to run multiple DOS programs simultaneously. OS/2's Dual Boot and Boot Manager features mean that you need not abandon an old OS completely in order to try OS/2.
Note that OS/2 applications can be hard to find, though they do exist; many software stores lack a good OS/2 selection, though this varies from store to store, even within a single chain. If you can't find a specific OS/2 commercial application, or if you simply want to know what's available, contact an OS/2 mail-order vendor, such as Indelible Blue (800-776-8284, 919-878-9700, 76256.3334@CompuServe.com, or fax at 919-878-7479). Even many local stores which don't stock OS/2 programs can special-order them, too.