Crop dusters a slow and the 5D2 will easily handle the AF chores there.
As an all around camera, I pick my 5D2 over my 7D almost all the time. It's high-ISO performance is superior and gives me more flexibility. Also, it suits my 24-105mm f/4L IS better as a walk-around, scenic and archetectural lens.
Still, when I've wanted to leave the Speedlite at home and use a pop-up flash, I've taken the 7D. I've found it no slouch at ISO 6400 without flash. Witness:
Michelle checks for text message...
, on Flickr
The 7D has superior detail resolution, thanks to its lower pixel-pitch, so in many ways it's a toss up.
I think it comes down to which lenses you already own and which body will take best advantage of them. The 7D is my go,-to on macro, wildlife and sports.
If you can wait, the 5D MkIII might be interesting. If they bring the pixel-pitch down to the level fo the 7D, like Nikon did with their FF D800, then you might have the best of both worlds in one camera. I'm holding off on any camera body decisions until I see the MkIII. I want to see real test of the 1D X and the 5D3 and then I'll decide between the 1D MkIV, 5D3 and 1D X. Of course, I'm already well equipped so waiting is easier.
Of course, anyone looking at my images should realize those are NOT out-of-camera jpegs. They all RAW, converted with DxO Optics Pro, which is like an upgrade for any body.