So you're saying you'd rather have your current unit repaired than get a new one? That's surprising. Usually it's the other way around.
Three weeks is completely believable to get a part in, especially if it's backordered. Remember, the part comes from the mfg. That's probably why they approved you for exchange, rather than making you wait three weeks.
After 2 Months I was able to get back my Laptop unrepaired. Now I contacted the Manufacturer directly and sent in my laptop to their repair center -- To my huge "surprise" they repaired it and sent in back to me in less than 7 days. I am after all happy that it was taken care of but raised a lot of questions about the credibilty of Best Buy/Geek Squad. I always liked how I can walk in to the store and ask them knowledgable people before making a decision to buy but I am not going to step inside a store unless I dont have any other options.
For anyone having issues that are within warranty period I would strongly suggest you go to the manufacturer directly than going thru Geek Squad.