I really don't like this trade, never have. Kevin is NOT on a bad contract- however much you don't want to trade him, he's not a salary dump player. The only condition you salary dump him is if you get a decent pick in return- not a late 20's pick like Boston has.
Plus, Ray Allen is good, but even if he stays he's only got 2-3 good years of basketball left.
I'd rather have actual assets than cap space, which guarantees you nothign.