Sure.
First, thermal management. I had an air-conditioning unit failure in the small room I kept the Pros in, as well as a number of Dell Poweredge 2850 servers and dual-5130 Precision 690's. The Pros were the first to go - in fact, they were the only machines to go. Only one machine actually had a PSU failure, but the others wouldn't run stable anymore after the incident.
Secondly, general OS stability. Sorry to say that I had significantly more (perhaps twice a month) kernel panics than on the Precisions under XP (three in total out of all the 690's I have so far I believe, and two of those caused while adding new gear) doing roughly similar things. The Pros are stock - no extra hardware bar the occasionally attached external drives, etc and they were still more unstable than the truly comparable XP installs.
Third, hardware issues. 10K drives start to give me resonance problems within the Mac Pro chassis. Some of the 690's started to give me resonance issues with the 15K drives which do run notably whinier/noisier but no problems whatsoever with 10K drives - despite the drive cage retainer assembly being basically a piece of moulded plastic. There's more but that's an example.