Earlier this year, Jeff Carlson reviewed the ViBook, a $129 device that enables you to add an additional monitor to any Mac (or PC running Windows) via USB (see "My Three Screens, via ViBook", 29 May 2009). Although Apple's desktop Macs now all support at least two monitors, and you can add oodles of them to a Mac Pro with the appropriate video cards, Apple's laptops are limited to a single additional monitor.

"Now," you might ask, "why would you want even two monitors on a Mac?" Productivity, my friends, productivity. Spaces is all fine and nice, but nothing beats having more screen real estate. I've been running multiple monitors on my Macs since my SE/30 in 1990, and I wouldn't use a single-monitor Mac for my work.

"Fine," you say, "but why would you want three monitors on a MacBook or MacBook Pro? Isn't that just gilding the lily?" Not really, and although I can't give statistics on this, my experience over the years is that two monitors that match in size and screen resolution (and ideally, manufacturer), positioned side-by-side, are better than two mismatched monitors.

Normally, on my 13-inch MacBook, I can connect one 24-inch display running at 1900 by 1200, but attempting to line that up with the MacBook's own 1280 by 800 display is awkward at best, and ergonomically evil at worst. Call me greedy, but if I were to use a MacBook or MacBook Pro as my only Mac, I'd want a pair of 24-inch displays, plus the laptop's own display.

A year ago, toward the end of 2008, when I bought my 13-inch unibody MacBook, I desperately wanted to make this work, but I just couldn't, because the ViBook at the time couldn't drive a display larger than 1680 by 1050. After researching all sorts of hacks, I finally gave up and bought a Mac Pro to run a pair of Dell 24-inch displays (which aren't as good as Apple's, but which do standard DVI instead of Mini DisplayPort and which cost about half as much). At the time, I was starting a new edition of my "iPhoto '09: Visual QuickStart Guide" in InDesign, and I needed all the screen space I could get.

Undeterred by the resolution limitation, though, Jeff Carlson gave the ViBook a try, and although he found that it worked, he ran up against a number of issues, including lack of 3D acceleration, an inability to color-calibrate the display, and relatively slow performance. These limitations meant it couldn't be used for iPhoto slideshows or Keynote presentations, or iMovie at all. And although video and games did work, their performance was often such that it wasn't worth using the ViBook-driven display for those purposes.

So when Harmonic Inversion Technology - VillageTronic's U.S. dealer - contacted us again to tell us about the $139 ViBook+, I jumped at the chance to test it. That's because the ViBook+ can drive monitors at resolutions up to 1920 by 1200, making it compatible with my 24-inch displays (it works with up to 28-inch monitors), and it uses a new DisplayLink chip that reportedly improves performance. Otherwise, and with the exceptions noted below, it's nearly identical to the unit Jeff reviewed earlier this year (so be sure to read his review if you're considering purchasing one).

The ViBook+'s installation CD didn't ship with a Mac driver, instead requiring a download, and there's only a beta driver available for Snow Leopard (scroll down to get the latest version), but it installed fine, and my MacBook immediately recognized the 24-inch monitor plugged into the little ViBook box. The Displays preference pane had no trouble seeing the ViBook-driven display and let me arrange it with the directly connected 24-inch monitor and the MacBook's built-in screen.

Although my beta driver didn't include any new release notes, I discovered that some of the compatibility issues Jeff had encountered had disappeared, though others had taken their place. iMovie launched, and appeared to work on the ViBook-connected monitor, though I don't use it enough to know if there might be further gotchas. iPhoto slideshows worked fine, though, strangely, editing did not.

Performance was totally satisfactory. I could tell, by grabbing a window and moving it up and down quickly, that the ViBook couldn't keep up with the MacBook's internal graphics controller, but it wasn't troublesome in normal usage. YouTube videos played acceptably in their normal window with only the occasional stutter, but expanding them to full screen failed miserably, with the video quickly losing sync with the audio. I don't play games, but I suspect full-screen games would suffer as well.

Luckily, these performance issues shouldn't really be a problem in most cases, since you can always just move the offending program to a built-in or directly connected monitor.

I'll note that although you can attach up to four ViBook+ adapters to a Mac, my experience is that unless your vision is extremely good, much more than two 24-inch displays side-by-side may prove hard to use. My eyes simply can't focus much further to either side.

Put simply, the ViBook+ is the product I wanted a year ago, and which I would have bought in favor of my Mac Pro. At $139 from Harmonic Inversion Technology, it's an inexpensive way to add additional monitors to any Mac, and as long as you go into the purchase understanding its limitations, you won't be disappointed.