I know this question has been asked over and over and several reviews on the web have put both cameras through their paces, but after my own use of both cameras, here is my 2 cents.
First off, let it be said that a FF 7D is the 5D3. This is not about comparing the these two bodies. The 5D2 is basically a FF rebel (in terms of speed/raw features), with a far SUPERIOR color processor and sensor! (No offense anyone)
I own both cameras. It comes down to this, if you are shooting mainly stills, weddings and "canned" shots, the 5D2 cannot be beat in areas of image quality and low light handling
However, for wildlife? The 7D is a workhorse and I love using mine. The more I shoot with it, the more I love it. I have been getting amazing images from it and it is far easier to use than I first gave it credit for. It is very fast and a "NOW" camera. It does what you want exactly when you want it done!
I am simply suggesting that a camera that can cost well over a grand less than the 5D3, and upwards of $600 less than the 5D2 and twice as fast as the 5D2, one has to stand up and take notice. When Canon does decide to make a "7D Mark II" they have their work cut out for them. For an APS-C camera, the 7D is as close to perfect as it can be and I for one cannot wait to see what they consider a "replacement" for the 7D! Yes, crop sensors have limits, just as FF bodies do... but the image quality and advantages (speed) of the 7D outweigh the 5D2 in real world shooting!
If you buy one, you will not be disappointed. I haven't been... (shots taken with the 7D, pics sized down for posting, full size rez photos are much, much nicer!)
EDIT:All of these shots were hand-held, no tripods, no "canned" shots. Ah, one more thing, the first 2 shots (macros) were taken with my beloved EF-s 60mm macro
, the horror!!!
I own the EF 100mm macro as well and I will not give up my EF-s 60mm macro for ANYTHING! Amazing lens!