I voted I do, but it depends, sometime DMing can become a chore, especially if you've started to lose interest in the current campaign. Say your stuck running D&D when you've just bought your D20 Modern rulebook and are thinking about your next campaign.
Really I don't mind if I play or DM, as long as I'm in the right mood for it. The advantage of being a player is that if you arn't in the mood that evening you can take a backseat and let the other 4 or 5 players take the lead and just take it easy. As a DM you never get that option, and if you don't put the effort into the game, then its likely the players will notice.