I aks because I've two T20s (one that's my main workhorse) and briefly had two T40s (until I returned them to the seller for a refund I never got - Chris Michael of Coventry, you are a bastard, a liar and no better than a petty thief), and I've found the all to be very decent to service. As far as PC laptops go, I don't think it gets much better than an IBM T-series. You can take them apart with one screwdriver, nothing's hidden or hard to work out. And of course (excepting the T40 models with the same ATI graphics chip that have the exact same issues as the iBooks!) they are incredibly reliable. I also very much like the UltraBay and the PCMCIA slots, when compared to the iBooks.
I recently took the HD out of a dead iBook and I hope I never, ever have to open one again, much less put it back together and hope it works! Why all the different kinds of screws? I don't understand it.