Now that I have the 1D X, the 7D just sits in the Storm case, keeping a few lenses company.
At least the lenses have a buddy now, lol!. To the OP, wedding/portrait/event shooter here. I tried using both my 7d and the mk3 during wedding season. After the first one I did like that the 7d basically became a lens holder. With a 24-70 on the 7d and a 70-200 on the mk3, I had some overlap on the long end of the 24-70. The only time I really had enjoyment from the combo was outdoor ceremonies. For indoors (I try my best to not use flash for ceremonies), I found that the high ISO performance of the mk3 was a real game changer. On the mk3 I could really go as high as i wanted in ISO, where to have a similar IQ on the 7d I had to keep it around 1600 (odd, before I got the mk3 I would go up to 4000 for low light, but after seeing the difference --- 7d ISO 4000 to mk3 ISO 6400 and above I found that it wa a waste to even take the time to snag a shot with the 7d ---just stick with the lens i had on the mk3 or switch lenses. And at a reception, forget about it, 7d just sits in the bag there.
I thought I'd miss the "range" of the APS-C, but I don't really miss it at all. I have the non-IS 70-200 2.8 and on the 7d to keep the SS at at least 1/100th indoors with no flash I had to pump the ISO up to at least 3200 ---the IQ just didn't stack up. On the mk3, at 200mm, ISO 6400, and severely cropped --- the image was nice and sharp, where the uncropped 3200 on the 7d looked muddy (the noise made me think my lens needed focus adjustment, i often looked at high ISO 7d images and thought it had missed focus, where in fact it was in focus, just reaaaaaaaaaaallly noisey)
I just sold my 7d to help fund the purchase of a second ff (either 6d or a second mk3). So I say, don't look back, go FF! you will be pleased!