I have 2 Pi's. I love them for what they are. What do you plan on doing with yours? One of mine I use for watching movies it runs Xbian and it plays 1080p movies flawlessly. The other runs Raspbian and smokeping which I use to monitor servers,routers and websites. I wouldnt recommend using a Pi as an everyday PC (but you could) due to its limited cpu and memory. I have had mine for over a year and they seem to be very reliable.
The one I use for movies runs Xbian and Xbmc, it works wonderfully. Mine uses a 8gb SD card with a 2TB USB drive. Also for your quadcopter check out Arduino pretty cool stuff. I have an Arduino mega board.