Hope I can help with the Best Buy deal. I did this last year when I upgraded from Instinct to my Pre at BB. Worked as good as it sounds. It did not take 4-6 weeks, it took like 2 weeks if I remember correctly. If you are part of the smart crowd that bought your device from BB, they will even evaluate and issue a gcard for your trade in on the spot in the store, so you can use it towards your EVO purchase price! This was mentioned at the top of this page, but many other topics have come up.
I verified this by going to the store last weekend. The procedure is just go to the Geek Squad section with your phone, and try to have all the components your cell came with: charger instruction book etc. Hello bucks! I believe what I saw was $113 BB card, and I'm currently sitting at $30 gcard for my rewardzone mastercard, so guess who's gettin an EVO for $60??? - This guy!
Best Buy is the ONLY way to go for maintaining the newest smartphone at the best price. End of story.