I upgraded from 60-70D, mainly for the AF, and for that the upgrade is HUGE. Image quality is comparable, but the noise pattern on the 70D is much more pleasant (at least to me), so I find myself using higher ISOs much more often. As far as wifi is concerned, I'm not using it nearly as much as I thought I would. I'm sort of disappointed that the wifi app only transfers smaller jpgs to your phone/tablet- which means other than simple social postings, there's not a lot I ever do with the images through wifi. I don't ever use the wifi with my computer since I can just take out the memory card and transfer files much faster. You can control the camera via wifi, but that's not something I've used yet.
I can't impress how much the AF is improved though- both in the viewfinder as well as live view. It's so much improved over the 60D, and that alone might make it worth the upgrade for some (but then again, so would a 7D). I'm not sure I'd upgrade just for wifi and slightly better low light performance. Actually, if all you want is wifi, I'd recommend a Toshiba FlashAir card, they are very easy to use, and although slower to write to than a UHS card, offer a better wifi transfer than the 70D. You won't be able to control things with it, but it's worked well for me.