Well, if you want to know my experiences with it, I think that it is a superb machine. Its held up for PS CS3 and my other uses (Final Cut). Web browsing is no problem. Comparing it to one of the earlier-G5 duals, its a cut above and beyond. Just be sure to fill it with as much RAM as you can afford and a TB HD... can't comment on graphics upgrades (got my machine with the 7800GT, never used the 6xxx series card that was baseline).
However, part of me does have to say that future OSX applications will be Intel-only. Doesn't mean you can make it a server with a RAID array after you are done with it.
Many people will say that a Mini is better (which its starting to look that way), but I think that the Quad should be a respectable machine for your needs in the timeframe you have to use it, and its not completely useless when you're done with it.
Just remember, despite reports of the replacements from the LCS failures in it, doesn't mean you'll get a new machine. Some people get replacements, some people don't. Be aware that if/when your LCS fails, assume you will be SOL.
