I switched about 3 years back. I was using PB12 then and PowerPC was already on its way out. I figured that if I have to get new software anyway, I may switch the platforms as well.
The Thinkpad T400 I got is still a good machine, 3 years later. So good, that my brother bought himself Thinkpad X230 and is satisfied as well.
I hear it. I'm a stickler for comfort and design, so I'll be going for the thinnest, slabbiest, least-dent-prone thinkpad I can find when the time comes. I really do insist on the slab - i.e. as few indentations as possible - approach, so I hope its considered necessary, somewhere in the future, by Thinkpad designers ..
The Thinkpad T400 I got is still a good machine, 3 years later. So good, that my brother bought himself Thinkpad X230 and is satisfied as well.