I received a new Dual 2.8 Mac Pro about 2 weeks ago from the Apple Store w/2 ATI 2600 cards to drive my (3) 23" Sony widescreen monitors. I migrated from a Dual 2-Gig G5 running Tiger to this system. I installed (4) WD 750-Gig Caviar RE2 HDs internally and 16-Gig of OWC RAM.
For the past 10 days I have been running ALL the CS3 apps (not including Acrobat Pro until todays release) - especially lots of After Effects CS3 and Photoshop Extended work. Of course, I have only been running the machine for 10-days, so it is still too early to tell if any serious problems will arise, but I have to say "so far" I have not experienced ANY "performance" issues.
I have had about 12 new Macs since 1985 (all top of the line) and I can honestly say that this is the first time I have seen a noticeable speed gain - and apparently in all areas! (and this is not top-of-the-line at 2.8). My restarts are taking about 30-seconds from selecting Restart to back-to-work (previously it took at least 2 minutes). Launching Photoshop with a ton of plugins and fonts takes 16-seconds as opposed to 1-minute previously. So, all-in-all (so far) I have been very pleased with the move.
I still do not feel totally confident with this set-up yet and backup every file to 3 locations every hour, but so far only experienced a Time Machine "cosmetic" glitch (which is apparently unique to me and Apple has no answers) and there are some issues with using Spaces with Photoshop so far (so I am not using Spaces yet). Since these processors, etc, are so new, I was very leery of this upgrade, but so far it has gone remarkably smoother than I anticipated (knock on wood).
I will say this much... IN MY CASE, I have never "yet" seen a single Apple HARDWARE failure in all my years (and I support a lot of local print shops and Ad Agency Macs for years). These are "machines" so there are certainly hardware issues that can arise - I just never have "experienced" one myself (yet). I HAVE had several print shops, Ad agencies, etc. over the years tell me that either AppleCare or Comp USA, etc. had diagnosed there machine as having a bad power supply or bad motherboard and it would have to be sent in for repair or replacement. IN EVERY CASE, I was able to go to their locations and get their machines up and running again without any "hardware" replacements!!! So, I know for a fact, that there must be TONS of Macs getting hardware replaced needlessly. That said, that may not be YOUR case! There may very well be a chronic issue with some of these new Mac Pros!
I am the first to admit that AppleCare is worthless. They have always been very willing to assist, but by the time you get through to a Senior Technician your tongue will be hanging out and to be honest over all my years they have NEVER been able to give me a fix for ANY issue I reported.On two occasions they said I apparently had a bad machine and they would replace it, but in both cases, I got it working on my own, because I did not have the time to wait on a new machine - it was always a software or hardware-configuration problem in my cases. The only reason I buy AppleCare is for that "disaster" when the machine "might" go up in smoke, but as far as fixes over the phone I have found them useless but willing to help.
IMO, "if THEY do determine" that a new Mac Pro needs to be replaced, I think they should at the very least cross-ship a replacement at their cost - especially in the first 90 days.
One thing that they will need to address on Leopard is the User Permissions problem that people (like myself) are having who "migrate" from a previous system. This could be a real sleeping giant if they do not come up with a fix to cleaning out the "unknown user" assignments. Of course, they have to admit to the problem first before they can issue a global fix.