Believe it or not, right now. At SC2004 we released PVFS2 1.0. We would be foolish to claim PVFS2 has no bugs and will work for everyone 100% of the time, but we feel PVFS2 is in pretty good shape. Early testing has found a lot of bugs, and we feel PVFS is ready for wider use.
Note that we're committed to supporting PVFS1 for some time after PVFS2 is available and stable. We feel like PVFS1 is a good solution for many groups already, and we would prefer for people to use PVFS1 for a little while longer rather than them have a sour first experience with PVFS2.
We announce updates frequently on the PVFS2 mailing lists. We encourage users to subscribe – it's the best way to keep abreast of PVFS2 developments. All code is being distributed under the LGPL license to facilitate use under arbitrarily licensed high-level libraries.