I don't hate Gomes, but I've always felt that he was radically overrated on this board (much like Delonte West). But that's not even the biggest reason why I don't want him.
Simply put, he doesn't fit what the Celtics need. He's not quick enough to be an effective defender against swingmen, which basically means he's another undersized 4 to go along with Powe and BBD. Furthermore, he doesn't have the range to play the 3 in this system. Remember, one of the reasons Posey worked so well here was because he was a good weak side 3-pt shooter. If you put Gomes on the floor with Rondo and Perkins, opposing defenses are going to have a field day cheating off all three of them to guard whatever members of the Big Three are on the floor with them.