26 month old iBook. Never had any problems with it. (It's used to make some "clicking" noises, which had me worried, but has actually stopped doing that, which I'm not sure if is a good sign or something that should make me really worried).
Actually I've never had any problems with the original hard drives in any of my (or my girlfriend's) Macs. I had one 3rd party HD that I bought and installed in my Pismo go bad, but even that worked well enough that I could take a complete backup before I returned it (after a year!) and got a new one.
I do consider myself very lucky in the HD department, though, and I'm pretty good at keeping current backups... 😉