I got into sound design when an open-source game I was on was flooded with composers, and we needed a sound designer. None of the composers on the game had anything beyond Finale but me, so I stepped up to the plate and haven't really looked back. I still write music, and would love to do that professionally, but I (currently) feel like sound design is the direction I'm going.
So, I was wondering, do any of you compose music as well as design sound? Did you start out writing music and moved into sound design?
UPDATE: Wow... I'm glad I'm not alone, but now I feel somewhat outmatched. :D