I've always been a fan of Hitachi (formerly IBM) TravelStar hard drives. Since their very first 7,200 RPM 2.5" drive, I've never settled for less in a notebook. They've also been VERY reliable for me, as I've never had one go bad yet. I'm currently using a 7K100.
I think more than 100 GB in a laptop is too much. That's a lot of data to put at risk of being on the road and such. There's also the possibility of theft. I've had plenty of Western Digital and Toshiba drives fail on me also. I'd rather go for speed and reliability over capacity.
If there's a 2.5" drive out there faster than the TravelStars, let me know.