1.) Dirk's game has never been reliant on athleticism - it's all skill, footwork and shooting. Compared to other guys who's game relied on elite athleticism (Dwade, Kobe), he was always likely to age the best. Look at Tim Duncan and Pau Gasol. The one area where his age shows the most is defensively, he can't move laterally.
2.) Chandler had a hybrid microfracture procedure where bone marrow was transplanted from his hip as opposed to a typical microfracture. It's still a fairly new procedure at the NBA level, but is supposed to have a much better prognosis.
3.) Wes Matthews did come back early, but its really not surprising when you consider the player. He's had his bumps along the way but I think he would've attacked his rehab the same way and been back on opening night on any team he would've signed for. He legitimately seems to hate not being able to play.
4.) Deron's still having the same lower leg issues he had in NJ and while there's a slight uptick in his scoring and FG%, I don't think there's enough to completely discount Carlisle's system and not sharing a backcourt with Joe Johnson.
5.) Raymond Felton was still fat and out of shape most of last season - he got a chance in the playoffs last and I think he's trying to seize the opportunity in a contract season. His numbers this season are strikingly similar to his last season in NY, though.