There are basically two main types of bullet players, granted, not everyone falls exactly under either category. The two are the tactical and sound players, who, regardless of the time control, think moves through and look deeper than most players. The other group consists of people who play good, but not great moves, very quickly. They depend on time to win, and often open very quickly, where sometimes they get caught off guard by an unexpected move. What's really annoying is that many times the, quicker and less accurate players ends up winning, not due to better chess play, but because they react quicker or simply throw moves out just to try to flag the opponent. Personally, I don't put too much weight into bullet chess, although it might be good for quick tactical practice.