I actually do think Al is underrated. Offensively he is the second best big in the game behind Cousins. He is one of only a handful of bigs you can just give it to in the low or high post and just watch him go to work...
But...
His passing is still very suspect and his passing out of a double team is borderline poor. Once Al gets it in the post he either has to do his thing or someone has to remain close enough to him to get an outlet pass if he gets doubled. Dude has been in the league forever and he still is not able to hit someone cutting to the rim. So while he can score in the post he also turns into a black hole on offense cause his passing is not good enough where other players can continue to set screens and/or make cuts and he can get them the ball, you end up with 4 guys just standing their watching Al trying to score.
His one on one defense is pretty bad, even by today's standards. He falls for way to many pump fakes and up and under moves.
Dude went to play for the Bobcats, on purpose, because they offered him the most money. So obviously Big Al doesn't care about winning, he just cares about getting paid. Good or bad, I think that for teams going for a title you need your best players to care about winning, and Big Al is far to talented in the post to be coming off any bench in the NBA.