I'd say I'm pretty good. Or at least, I've never had players complaining or looking anything other than excited when we get ready to game. Also, hearing the players talking about the games in real life always seemed to hint that I was doing a good job.
Of course, I'm not perfect. While I love completely winging it, that can slow things down if the "Hey, why don't I do this..." takes a little longer than usual. Probably should also make flowcharts of my crazy ideas as I think them up so I don't forget small details, too...