I'm a software dev. for a medical device company and when I read pg's comment about the mismatch between startup culture and government culture, the first thought I had was "add medical to the list."

The medical device/software field is certainly interesting, exciting even at times, but it progresses at an absolutely glacial pace for the most part. You're dealing with slow, conservative institutions (hospitals, etc) and government agencies. Unless you hire people specifically to deal with those soul-crushing interactions, you'll probably want to shoot yourself.