1) XFS has just been released - no significant testing has been done. Before anyone can entertain the suggestion that XFS is the best journaling system around they should have a large volume of test data to support such suggestions.
XFS has been used in enterprise level environments (on IRIX) since 1994. I'd call that pretty significant - certainly more than ReiserFS has been subjected to. The gap in the XFS solution is the link between the fs and the linux kernel, and that's what SGI have been working on for the last year or two. I'm sure they have it pretty stable for v1.0. Of course, ReiserFS has only been at 'v1.0' since the advent of the 2.4.1 kernel, so the same applies there I suppose. As far as I know there isn't a large volume of test data for either system on Linux, at least not public. But if SGI work like we do (I'm at IBM's Storage Systems Group) they'll have put it through more formal testing than Reiser will ever be able to do. I suspect most people on this list are used to desktop PCs. One look at our test lab would make the jaws of most people from that background drop. I wonder if ReiserFS has ever been worked flat out by a 24 CPU machine like the one not 3 metres from where I'm sitting right now? I know JFS has on AIX ('cos I ran the test!), and the Linux version will too, before it ships as v1.0. I suspect SGI have similar procedures. That's the benefit of having a multi-million dollar company behind you. I don't know how Reiser test their product so I'm not going to knock them, but your claim that there has been been "no significant testing" of XFS on Linux is almost certainly way off.
2) ReiserFS has been on SuSE since 6.4 and, for example, is being used in production where I work. It's been up since Sept 17,2000 without a crash or data loss. And, my Microsurf co-workers insist on rebooting it every week in order to use Norton's Ghost to mirror the HD. That's 28 reboots without a failure. (I wish they'd have used a Linux backup utility like tar, but they carry with them a distrust of software stability earned through long experience with WinXX.
Does ReiserFS serve NFS files yet? I can't - not won't, but can't - use it until it does. And I mean reliably, not some hack.
While milage may vary depending on the hardware envolved, and the configuration of Linux and its supporting applications, anecdotal evidence like mine is better than the blue-sky theory which is all the XFS has for support.
See point one. XFS and IBM's JFS have been around for years. From the ramblings of Hans Reiser which I've read I know who I suspect as having "blue-sky theory". (Go to http://www.namesys.com and click on the "Future Vision" link. The guy clearly has a brain the size of a planet, but I've never been quite sure his feet are on this one!) Disclaimer: I speak for myself and not IBM. None of the above should be taken as indication of IBM policy or practice.