A few months ago I bought a kit from Sparkfun to mess around with. Got everything built only to find out that something was wrong with the FTDI (I couldn't upload new sketches). After a quick e-mail exchange, Sparkfun sent out a whole new board.

For people who don't know much about hardware, that kind of customer service is invaluable. Without it, I could have spent days trying to figure out what was wrong, only to give up in frustration. Instead, I got quick confirmation that there was something wrong with the board and was immediately sent a replacement (at no extra cost).