I think it is only disappointing cause everyone had such high expectations. After all the kid is still only 21, and didn't pitch full time until the minor leagues when the Dodgers converted him to a SP. Right now he lacks control (which the dodgers may have some hand in when they changed his delivery) and the knowledge of how to really pitch, things you can't do while your in AAA or the majors.
Early on in the season he had some good games, mostly away from Las Vegas (or as I call it AAA Coors). But eventually I think his confidence was shot down and then the promotion of Thompson instead of him evidently really hurt him from what I have heard. Honestly this is the best move for him, he is still young for AA and he gets to start over and get out of LV.
Personally even though I haven't been a big Gavin Floyd fan, he has disappointed me more then Edwin. While he is still young, he is a year older, hasn't been rushed nearly as much, doesn't pitch in a hitters league/park, and has a better feel for pitching. I though he would at least be posting some solid/average numbers.