I've only umpired in friendlies for 10 overs or so but I do find it more interesting than sitting in the pavilion. Having read through this thread I'm amazed how many players think it is a good idea to moan at an umpire and get on the wrong side of him.
When I'm keeping I try to put the bails back on as much as possible so the square leg doesn't have to come in. I also run to the umpire to hand him the ball when a wicket falls. When I bat I try to strike up a conversation with an umpire. It must be nice to have a chat with a player and secretly I hope he might give me the benefit if he likes me.