I was advised that 7200 drives are noisey and can get hot, and was told to buy a 5400, as they dont get hot and are very quiet.
the guy i spoke to said you only need 7200 in a PC, hard drive recorders dont need to be that fast
its true, never had a problem with mine at all..... the ultimate test was recording a program while watching another from the hard drive at the same time!!!! and it worked too.... no glitching or anything

even on the recorded program.
Only problem is, 5400 are pretty hard to get hold of now