I work for IBM and have been using Thinkpads for 15 years now. When we owned the Thinkpads, there was a quality issue with some of the parts and mostly with the harddrives. Since Lenovo has taken over (we are still required to use "Thinkpads"), I have noticed the quality has improved greatly. I currently use a T-60 (for 2 years now) and before that I had a T-40 (for 3 years) and I have never had to replace anything and my boxes get used an average of 10 hours a day ... every day. With the T-60, I occasionally have to clean out the fan and fan vent area, but as eagl has pointed out all I need is a simple screwdriver and in 10 minutes all is clean and back together.
I work in a group of around 30 people and most of us travel quite a bit, and all around the world, and I can say with certainty, that these boxes are road warriors. A couple of people have spilled their drinks on the jet all over their keyboard which caused problems, but with new keyboards overnight-ed to their hotel, they were up and running in no time.
I have a friend who sent 2 boys thru college with Thinkpads (same Thinkpad for 4 years) on my recommendation and each of them said that their Thinkpads were work horses and tough as nails ... where their friends had to practically buy new laptops every year.