My only experience is that with my HP warranty the service was substandard. It was a high end business machine and I was without it for two weeks after I finally convinced them it wasn't a software problem.

I have had a few experiences with Lenovo with the various laptops I have had from them. While I haven't had anything happen in the last three years or so, when I did have to use them it was either 1) they overnight a box to me, I overnight it back to them, they fix it in a day, they overnight the laptop back to me; or 2) If it is a user-serviceable part they had no problem overnighting the bad part to me. I seem to remember interacting with IBM out of Georgia. Couldn't tell you if that is still the case.