Honestly, my initial reaction to this is "gross". Really, why do we need to sign a player who clearly has very little between the ears and has proven over his career to be a waste of any sort of talent or athleticism?
But I guess when I think about it a little more, it doesn't bother me too much. There really is very little risk in signing McGee. If he turns out to be the bum he always has been it's not like he's costing the Celtics much in the way of financial flexibility or assets. If he somehow turns his career around with the Celtics, well, Ainge has managed to acquire yet another assets for next to nothing, a la Jordan Crawford.
So yeah, I guess I'm hoping McGee can at least play well enough to become a tradeable asset. That's the best case scenario I can imagine, because I don't see any way he'll ever be in our long term plans, there is just too much evidence he's not a good basketball player. But GM's get doped all the time by the promise of tall, athletic big men, so I could see a scenario where Ainge could take advantage of that.