My point of view is that the Wizard is fun to play, and perhaps the most customizable Mage (due to training selections). I, however, have to suggest that the Wizard isn't over-powered. I believe that a person's skill in general, and familiarity with any Mage in particular is what is important.
I have a friend who regularly beats me... and I don't think he's played a Wizard more than once or twice out of all of our matches, while I play one at least half of the time. Sure, the Wizard is good when played by someone who is very good at the game, knows what to expect from his or her opponent, and so on... but then most Mages are.
Conversely, if the Wizard is going up against another Mage who either 1) casts creature after creature while minimizing enchantments, or 2) goes all out aggressive on him, then the Wizard can't play such a game with multiple dispels and dissolves, or in gaining extra mana... he'll not be able to keep up in the damage dealing race. Having more mana in the end doesn't matter if you are dead.
In particular, I like how AW went about making the Wizard (primarily) somewhat less powerful, and helping the Warlord out without messing with the design of the Wizard directly. The runes were brilliant... making it more costly to remove equipment, etc. so there is a better balance there... but please don't tell me that a well-played Warlock or Forcemaster or Beastmaster or Priestess or whatever is underpowered compared with an equally well-played Wizard. I don't buy it.