My T61p lasted well it's 4 year service life, only issue I had with it was the backlight starting to fade. Some of my co-workers have had issues with their T61p motherboards, but only really around the 4+ year mark.
I just got a W520, which has been great, with the exception of Nvidia not bringing Optimus support to Linux... And I replaced my wife's Acer with a x120e, and it is doing well under Ubuntu 11.10
The quality may not seem quite as high as the IBM days, but I still remember a rash of motherboard replacements on T41 laptops, mostly with failed USB ports. I even had a motherboard delivered via UPS Sonic Air (same day courier) for a critical laptop issue.
After being inside IBM for the last few years, I can say that IBM really understands Enterprise, but if it's not low volume, high margin, and cradle to grave, they can't make money on it, with the exception of services. IBM is contracted by Lenovo to provide a lot of Lenovo's support services.
AC for good obvious reasons.