I might give him a little clap at the start, if I'm in a good mood, and that would be it. I won't boo him at all because it's unnessecary, and, also, he wasn't THAT bad during his time here. I admit his performances weren't great, but he only played 24 times in total in a league he hadn't played in before, and he had injury problems, so maybe it's a bit harsh to hate him for that. Who knows what might have happened if we had kept him and he'd stayed injury free, he could have been a great defender for us.
Also, when the biggest club in your country come along, and tell you they will play you in your best position and you aren't guarenteed regular football at your current club, then there is always going to be a decent chance you'd leave. It would have been nice to see him show some determination and fight harder to be successful here, but in that situation a move to Bayern would have been very hard to turn down.
So yes, I will briefly applaud him then treat him like he's just any other player through the game, unless he does something to annoy us, although I don't see why he'd do that.