Sounds very promising?
Does it seem to work qith the Redhat confifurations listed? Yes.
Have I really tested it? No. And I'm unlikely to say "yes" until one or seven things have blown up on me.
In the long run, I think XFS will be an excellent addition to the stock kernel offerings. Right now we're in a situation where XFS is a part of niether the main kernel tree nor any standard distribution offering. You will have to balance its possible benefit against the maintanability of your particular installation (or, more likely, installations). As an aside, my preference is currently for BSD operating systems that make use of FFS over Linux distributions, if only for reasons of stability.
Also, neither ReiserFS nor XFS seem to provide much perfomance benefit to database applications right now -- or at least no more than FFS with soft updates does. The performance gains from hashed directories barely affects the small number of files used in openacs/opennsd/postgresql. As for the reliability factor of a journaling filesystem... that has yet to be proven with these implementations and this particular set of software.
I used it since early beta stages (on test machines) and have recently deployed it on a production server. It works beautifully and it was very stable so far. It's backed by a team of clueful developers and has a pretty impressive QA test suite, and it's been used for years in IRIX, so I'd say it's a quite solid technology.
XFS stability on IRIX does not necessarily connote XFS stability on Linux. I worked for five years at SGI and from my own personal experience with IRIX, I would be very wary of x.0 software from SGI. XFS debuted for IRIX 5.3 (maybe 1994?) and wasn't particularly stable in the 1.0 release. At least two of my IRIX systems running XFS had their drives destroyed when meta-data got corrupted. Version 1.1 of XFS (IRIX) was much more stable and when kudzu (IRIX 6.2) released, it was pretty much ready for production use. XFS on IRIX is now mature; combined with XLV, the logical volume manager, it really rocks, too.
As a former SGIer, there's no way that I'd put XFS 1.0 on a production box. I'm running ReiserFS myself and I'll switch to XFS when it's proven (1.1 maybe).