For the record I bought my SB at Best Buy, and I just had a very positive experience at an MS store. My SB recently developed some pretty bad light bleeding right around the top center of the screen - near the camera. I took it in to the MS store expecting to have to fight for a replacement, but it was quick, painless, and very hassle-free. Basically the conversation went:
Hi, my name is XXX, may I ask your name?
Jim
Hi Jim, what's the problem?
I have some light bleed, let me show you (shows the screen).
(MS employee glances at screen) Yes, that's pretty bad, let's get you a replacement. I'll be right back and YYY can help you if you have any questions while I get a new machine. (heads off to grab a brand new SB)
At that point another employee came up to me to ask if they could get me anything while I waited and went and brewed some hot green tea for me. We were about half way through the return process before he even asked where I bought it and didn't balk at all when I told him Best Buy.