I never had too much fun with that. As a pokemon, you are the smallest possible size running around looking for something to do until someone throws a ball at you and catches you. Then you're stuck watching that player run around for ten minutes looking for something to do, until he throws you at another "pokemon" and tells you to fight it. So you kill it with a sword and then your "trainer" puts you back in the ball and goes AFK for half an hour leaving you to just sit there starring at his avatar. As a trainer, you just run around looking for tiny things only a little smaller than a 1X1 brick to catch in your little ball. You will probably never find any pokemon, because being a pokemon is so frustrating most people will probably just switch over to trainer.
Yet everyone loves it.