It is largely anecdotal, but you do see a lot of the same issues come up. I bought an x220, and a year later I've sworn off Thinkpads. The palmrest has cracked - a common problem for the x220, documented on forums - and Lenovo refuses to fix it. Similarly the keyboard has turned to complete mush - whereas my old X60 keyboard still feels good as new. The entire chassis has warped over time as well, which means it doesn't sit completely flat on a surface - another documented issue on thinkpad forums. And my first battery, a 9 cell Sanyo, died after about 9 months of careful use - again a well known issue on the forums.

So this is why a lot of people perceive quality has tanked at Lenovo. IBM thinkpads did have their own problems (like bad screens), but in general were built like tanks and lasted years.