I answered very similar questions below in response to davidw, so look there for a breakdown. As for the experience I am looking to get out of it... hard to explain exactly. I just find the idea of working with a small group of developers on something innovative to be extremely appealing, and the risk/reward ratio of startups to be satisfying as well. I would much rather work for a startup with a chance to make it big (and a considerable chance to fail) than work for a corp with a guaranteed chance of office politics and mindless drudgery.