I've had a 5400 Travelstar 40 gig and a 7200 Travelstar 60 gig in both my old 400 Tibook and my 667 Tibook DVI.
The old Toshiba/Fujitsu 4200 drives were of course slow but, I like quiet, and they were noisy suckers.
Travelstars are quiet and I did notice the biggest bump from 4200 to 5400. On the 7200 now and while faster, not noticably more than the 5400. My fan RARELY comes on. I mean RARELY, so heat is about the same. I was initally worried about heat last year when I got the 5400 but just buy an iStand or better yet a Macally ice pad -- round 20 bucks -- to keep the Titaniums cool.
Wish I'd gotten a 1 gig Tibook -- to me they are the high point of the apple powerbook line, sorry ALbook owners!