I've owned the XD9 for ~ 2 months and very satisfied with the keyboard. The only reason I personally would trade up to the SD1 would be for the 76 keys, since I'm a piano player. Another reason might be for the audio/wave file usage, however that's somewhat limited now in the SD1. If you're happy with 61 keys, then I'd say the XD9 would be a great "can't go wrong" choice.

Glenn