Can I get a replacement Xbox 360 while I wait for mine to be repaired?

Microsoft isn't going to send you out an immediate replacement. Their procedure is to check out the 360 that you sent in to make sure that it is covered under warranty. Because you are sending it in with the RRoD, they will send you back a refurbished 360 after they make sure that the RRoD wasn't caused by something that you did. They say that it takes 4-6 weeks to get the replacement, but it normally only takes 3 weeks. Unfortunately, still not in time for Christmas. Sorry.