I would boo him. I don't have to look at the NBA like it's a business I look at it as a passionate fan. He left to go play with a hated rival. That's why you have to love KG. He could have played that buisness card and recieved much more money else where and shopped himself around but he truly loves playing for Boston and accepted much less. This is all my opinion so don't jump all over me.
The other side though is that Ray has wanted a multi-year extension from the Celtics for some time now, and the Celtics didn't offer. Instead they tried to trade him, multiple times.
Even as a passionate fan, I can't fault Ray for taking his time right now and exploring his options.
It's just the "going to the Heat" possibility which rubs be the wrong way, but this whole playing the loyalty card, that he somehow has to sign for us out of loyalty is misplaced in my opinion. But going to the Heat is a bit of slap in the face to me, even if I've never met the guy.