Trust me, you don't want it... At least not with graphics switching in its current state.
With my MBP, it's a pain to deal with: the discrete GPU runs hot as heck and destroys battery life (drained twice as fast).
That would be mitigated by the graphics switching if it worked as I expected: namely only when the HD 3000 is not enough, but in reality, the dGPU takes over too often. Even Chrome and MPlayerX trigger it for no apparent reason (the HD 3000 would be plenty for them).
Thankfully, a band-aid exists and works well:
gfxCardStatus. However, it introduces another problem: with one of the GPUs active, apps begin to use that one, but then when gfxCardStatus switches to the other one (for example, when unplugging the power adapter), those apps are confused and try to use the GPU that just got disabled, leading to missing Flash videos on Chrome, or a black screen on MPlayerX (audio plays fine). One has to restart them for them to pick up the newly active GPU. It's a right PITA. The only one though (on the 2011 15" MBP).
Dealing with this sort of shortcomings doesn't sit right with me on the Air. To me, this MacBook lineup is all about slickness and simplicity. It should keep things simple: only one GPU until graphics switching gets polished.