On the other hand, the 133 IDE drive in the G4 Power Mac we have in the office doesn't seem slow at all.
It just seems to be games that suffer from the obvious effects of slow hard drive access, leading to stuttering and long load times. With apps it just takes a little longer for them to start up in the first place and I suppose if you're low on memory, using the hard drive as virtual memory would be slower on a 5400 drive.