Favre coming back was a poor decision on his part motivated by self-interest. While I can understand where he's coming from, I think that it was a good idea for the Packers to tell him "please don't come back", and then when he forced their hand, to trade him to the Jets.
He's done this for a few years now, always causing a ruckus by "Oh golly, should I retire or not?" and it was getting tiring. Either say you'll do something and stick with it, or don't do it. The Packers, at some point, needed to move on rather than let him distract the locker room during Training Camp another year and allow him to cause a dramarama. As such, I think they made the right decision.
Favre, meanwhile, has GOT to be regretting this, as he will soon be killed in New York by rampaging defensive linemen. Hopefully at some point he realizes what a nonce he's been about retiring/not retiring.
He's a great QB, but, for god's sake, make up your mind sometimes. Is he the same way with his wife in bed? "Honey, let's have sex tonight. Wait, well, no, I mean, I dunno, I'm feeling old and rusty, and my joints hurt. Should we? We should. But man, I don't want to get injured and be handicapped for life..."