Haha, just noticed this thread was started in 2011!
I have to say I've always had good luck with Advance, to the point that its the first place I go when I need stuff. Of course, I've never made any large purchases (engines, transmissions, etc), but the counter people have always been helpful. Now, a buddy of mine has had an interesting time getting a rear axle for his 4x4 Chevrolet compact truck. He bought the truck off CraigsList, and the rearend went out within a week of owning it. He bought a used replacement axle through Advance, and it started roaring itself within a week. Advance warrantied it, and sent another used replacement. Being the smart guy he is, they pulled the pumpkin cover when it was drop shipped and found just about enough metal chunks/shavings to build another gear set! Needless to say, he is awaiting another rearend!!