I enter beers into competitions for feed back. Feed back is given by humans and therefore the quality can vary. I also like to try and enter the beers I think a really good into a couple of competitions. This allows me to get more of an average on the feedback notes. It also helps me to start recognizing when that particular beer is getting past its prime. If you brew a beer that you can taste mild flaws in I wouldn't bother with entering it. I only enter beers I believe to be dialed, and hope to get some feedback that can make them even better. This year for first round one of my entries was a German Pils. I felt that it missed the mark a little on hop presence so I decided, last minute, to enter it as a Dortmunder as well. It took first place in the light lager but scored poorly in the pils category. So, once you've decided its good and there's not detectable flaws then you have to pick the appropriate category or all is for not.