I was a network engineer for IBM, and used a TON of their Thinkpads, and am typing this from a T43. I received them free, so I beat the living hell out of them. I've dropped them 6 feet to concrete while programing Cisco switches OFTEN. One time, the case popped open exposing the logic board, I banged it shut, and kept on programing without a hiccup. These things are built for work, and proper battle.
Highly recommended machines.
I will say however, I've noticed the build quality go down hill slightly since the leveno stuff started to dominate. I may be wrong, but still worth noting.