I recently posted in the below threads about this topic.
https://forums.macrumors.com/threads/444663/
https://forums.macrumors.com/threads/560455/
You can read them for a more detail response, but basically, in short, I have the new macbook air 1.86 notebook with 9400M gfx chipset. Overall, it does run Maya and runs it fine. So far, to my surprise it actually works pretty well. I was setting up a 40k poly character in Maya fine and painting weights with Artisan no problem. My previous notebook which also run fine for maya used a 6200M mobile gfx card and that is slower than the 9400M gfx card, so I knew if the drivers were decent, the new chipset will be fine.
But, if I was actually doing work, I wouldn't use 9400M based gfx cards. They are okay and workable and stable enough, but small things like viewport interactions, panning, orbiting the camera, sometimes will not be as smooth as a real desktop video card. There are tiny bit of lag or choke here and there that makes the experience not as smooth or fast but it is by no means cannot handle it. Like I said, I can scrub through animation, setup, animate a 40k poly character in maya 2009 with no problems. So that is pretty good imo.
With your situation for work, I would not recommend it. You need at least a real desktop gfx card for work imo.
And yes, I too am pretty disappointed with the new imac as well. Basically they have been refreshing this imac with minor upgrades for a long while now and this upgrade doesn't even have much performance gain... I was really hoping for the core2quads to come out with this latest refresh....
Hope it helps.