I've owned two 7D's, two 5D MK II's and two 5D MK III's. My 7D was mostly useful as a studio camera with good lighting, or outdoors with bright lighting. It suffered at high ISO 800 or over, but could be used at 1600 or even 3200 if you were immune to noise or used a lot of NR.
I always preferred my 5D MK II to the 7D's. Finally, I sold the 7D's and bought a used 1D MK II. What a improvement that made.
The 7D was certainly a good crop body, it had some significant good points in adequate light and suffered in low light.
BTW, you need only look at the resolution scores at Photozone, DXO, or any lens review site to see how much sharper FF images are than images from a crop camera. Even a old 5D classic will out resolve every Canon crop made including the 7D when tested using the same lens. The reason is that FF cameras are not as demanding of a lens as a camera with a small sensor. Just because a crop uses the center portion of a lens does not overcome the FF advantage except for vignetting.