Just some personal thoughts/opinions here...
This past weekend I shot with both my 7D and my (well, girlfriends) T1i, both equipped with L lenses (24-105 and 70-200). Over the course of the evening (zombie walk, check flickr for photos) I was switching between the two constantly. When I originally got the 7D I never noticed how much faster the AF was, or how much more accurate it was. However, I always appreciated the ease of using the system as a whole with the various AF modes, servo tracking, etc...
But looking through my results, the 7D fared much better with servo than the T1i with the same high quality lenses. Not to mention in general, can lock much faster in lower light (different test, but worth mentioning).
I then looked at some old photos from Cedar Point (amusement park, for those who live under a rock!) taken last summer when all I had was my Xsi/T1i, and notice simply, my AF lock on rate was just not THAT accurate. I mean, sure it did great but just not as good as the results I get now. Some sharp, some soft, some in the middle. Now, you really have to try hard to get a soft photo (honestly!).
Simply put, I never did notice all the improvement in the AF system as far as accuracy until I compared firsthand the results after a few months. Not only that, but the IQ even at 100% crops (for peepers!) are superior to that of my Xsi/T1i photos, even with the larger resolution and highly pixel packed sensor.
Just wanted to share some thoughts though... The 7D is just a pleasure to use in so many ways. It really was designed for maximum efficiency and ease of use to the photographer. I never feel I work for the camera, but that the camera adjusts and works with me.
For those debating about this wonderful body, just do it. You will not regret it.
Now.. We just have to hope Canon can/will throw this AF in the 5D system and create the ultimate camera body (for now). I would be first in line for that one! 
Thanks for reading!
