Just hit 40 when I completed Act I NM.
My DPS, apparently, is pretty low: 1300 DPS, 3.5-4.5k Health. However, I burned through Act 1 without any deaths (including quite a few Champion/Elite Packs) in about 1 hour.
The spec I'm using is:http://us.battle.net/d3/en/calculator/wizard#UiXRmS!YcV!bbZbaZ
Probably unorthodox, but it works for me: I lighting blast the enemies down (stuns pretty frequently) and Disintegrate them for the +395% explosion. If things get really hairy, I'll pop Archon right on top of them for +450% with the pummeling attack/Jean-greay-beam-of-death ability.
I use Diamond Skin as an offensive CD, for the 7 AP reduction on my Disintegrate beam, which makes it almost infinite for 6 seconds. I'll pop Hydras when I need more DPS against single target. If I'm going up against a boss, I'll change out Disintegrate for either Ray of Frost with the +280% damage Rune or Arcane Orb with Obliteration Rune.
So far, it's worked really, really well for me: most enemies die instantly. I do get hit, but not long, nor very often. I'm thinking of upgrading my weapon, though my Rings/Amulets are in need of the most upgrade: no + damage on either of them and pretty low level.
My weapon is 60 DPS, (6-7 damage, 40ish int, socketed for 10-20 damage); offhand is 10-17 damage (20ish int, socketed with int) and all my gear has int, of some value, on it with vitality.
I only have 100k gold, after spending about 150k for the Whimsyshire staff... so I'll probably try and get through Act II before another gear upgrade.