I always say you can't judge a GM by each individual move he makes, but rather on the net effect of his moves. Certainly Ainge has made some errors in his tenure (giving O'Brien an extension, resigning Blount), but even with those you can see his rationale.
For point of reference, here is the team roster and salary cap situation at the beginning of his tenure and where it is now:
Before Danny: June 8, 2003 | Now: June 1, 2005
Which leaves us with the next obvious question... what next?