I've never had any issues with Maxtors that was not attributed to stress from an overclocked FSB. I have had to RMA quite a few WD's at work though, but these seem isolated to their 2mb cache 40g model.
I also happen to be in a unique position where I actually own the 80g 7200rpm version of Maxtor's, WD's and Seagate's 8mb cache HDDs (the Seagates are $59.95 after rebates at CompUSA this week).
As far as I can tell, here are the most noticable differences:
Most quiet = Seagate, by a hair. Maxtor is right behind it. WD is dead last, but bear in mind, it's still a fairly quiet HDD.
Performance = Using HDTach and Sisoft under WinXP, the Maxtor is markedly faster than either WD or Seagate. Between Seagate and WD, performance is roughly equal. I think these benchmarks utilities may tend to favor the Maxtors more so then the other brands since the Maxtors are the only ones that are ATA133 compliant. Unfortunately, I don't have any comparitive benchmarks here at work right now. During actual use though, there was no noticable difference between any of them.
Fit and construction = Although not a very good barometer for measuring durability, it's better than nothing as a sloppily built HDD generally means the overall Q/A may not be as good. Here, the Seagate is head and shoulders above either Maxtor or WD. Some of the stories I've heard about Seagate's excellent quality definitely shows. The tolerances, fit of parts, precision of build, and just flat out polish that goes into the contruction of the Seagate is just incredible when compared side by side with the other brands. It's like looking at a swiss-made watch and comparing it with a $20 supermarket CASIO. I especially like the precision fitted, protective plate mounted on the underbelly of the HDD to protect the HDD PCB and to keep foreign debris out. I guess you really do get what you pay for.
Heat = couldn't really tell the difference between any of them. All run warm, but not hot.