He's a top 5 GM in my book and I think C's fans are extremely fortunate to have him. When you look at the landscape of the league, we're truly blessed to have both great owners and a smart GM. That's why I have faith we'll be back soon to contention. They know what they are doing.
Ainge came in 2003. He tore the team apart and within 5 years he brought a championship and 5 years of legit contention. You can argue some of his drafts haven't panned out (Giddens, Melo, etc) but you also have to factor in the position he's been drafting (late teens/20's).
As for trades, I supported the Perkins deal. Ainge bet on Shaq and that gamble didn't work. But that team wasn't going to go anywhere without a legitimate backup for Pierce who was being run into the ground. And looking back at it, Ainge won that trade Green is a much better player than Perkins. Also, the PP/KG deal to BRK might be the heist of the century if it pans out like we hope it does.
Overall, people don't like him because sometimes he's cold blooded. But that's how the game is played. He's a good GM in my book and I'm keen to see what he does with another potential lottery pick this year and cap space.