Greetings!
As one who has competed often at different levels, both as an individual and as part of a band (waiting to work up the guts for bodhran and whistle - they can't be THAT hard, can they?) I can empathize with you. What I have found is that forums where the adjudicator is required to write a critique while you are playing tend to be much better at helping you hone your playing than the ones where they simply post results after. With written sheets (although I haven't seen them at folk contests I've watched) you at least find out what they thought of the performance and maybe get a basis for why you've placed where you did.
On the other hand, having adjudicated contests where the entire field of 10 to 20 players were pretty bloody bad, contests can sometimes come down to which player made the fewer basic errors - not who played the best.
One contest, a pipe band snare drumming contest I judged, saw five or six players comparing sheets and griping about all getting the same comments. At the end of the day, I called the lot of them over and went through exactly WHY they got those comments - because they all had the same basic problems. I then dressed them down for improper etiquette and talking loud enough to be heard while a soloist in another grade was playing "on the boards." They liked me even less after that - by which time I did not care.
MMario - I like your response - sometimes that is a better prize that a little cash quickly spent in the beer tent or a bit of hardware that hangs on the wall or gathers dust on a shelf.
Regards -
Pete