While it worked acceptably for three years, I gave up on my Thinkpad W520 this summer and switched to a Macbook Pro. Partly it was due to size (going from a bulky 15" to a really slim 13" computer is awesome), and partly it was due to wanting application support again, after seven years of almost exclusively using Linux.
One thing I'd like to say when looking at Thinkpads, or other laptops, for running Linux on, don't get one with hybrid graphics. My experience in trying to deal with it was a huge pain.
Maybe my problem was in going for the W-series. The older T-series laptops I've installed and used Linux on were great.
My T42 worked like a dream on Ubuntu 14.04 until recently, and now it refuses to awaken from sleep properly at all because of some update or other. I'm dreading trying to track this down and possibly finding out I'm stuck with using Windows 7.
I had (well, still have, but don't use) a w510. It worked just as well as the t61 before it (which was to say, they both did great under Linux), but it didn't have hybrid graphics... it was Nvidia all the time. The only reason I've replaced it was that it had absolutely abysmal battery life. Old job bought me a comparable ultrabook that weighs 20 pounds less and has 3x the battery life and I couldn't be happier.
I have a T430s - fairly thin with hybrid graphics. You should know that you can switch off hybrid graphics in the BIOS. Please feel free to get a hybrid graphics thinkpad - you can use it whichever way you want.
One thing I'd like to say when looking at Thinkpads, or other laptops, for running Linux on, don't get one with hybrid graphics. My experience in trying to deal with it was a huge pain.
Maybe my problem was in going for the W-series. The older T-series laptops I've installed and used Linux on were great.