I have the 60d and was wondering if it was worth getting the 70d? I am shoot weddings which are dark at the receptions. Is the 70d low light performance that much better than the 60d to upgrade to?

Jeff the 70d is a brilliant upgrade but not the best in low light, also if it is not a stm lens then you will here the noise of the focus hunting.. I use voice recorders so i am OK in that regard but? I have c100, two 6ds and two 70d which in good light are getting used far much than the others, 70d is simply a dream with the auto focus and flip out screen. You will not look back. We switch to the c100 and 6d after the ceremony. Steve

Steve, what specific lenses are you using with your 70D that are quiet?

I've tried a few, some STM, and haven't really found one I'm happy with.

None Robert, we use the 17-55 2.8, the 50mm 1.4 sometimes, sigma 30mm 1.4 but the 17-55 2.8 mainly but you can here the noise, so i put a voice recorder on me and record the whole prep if i need the audio.

The 70D allows you to spend more time composing and being more creative, as opposed to constantly struggling with focus. And if operated properly, you can trust the focus. You just have to know which mode of focus to use for which situations, and program a button that can disable it temporarily when you want focus locked.
The 70D has displaced my 5D as the A camera, and it is really liberating to use.

+1 Brian Spot on

Of course, a big part of manual focus is practice, practice, practice.

My son and his friend shot a wedding on 5D2s recently. The friend, with little experience, shot with a 16-35 on a tripod. My son, with much more experience, used a 100/f2.8L IS on a steaditracker wide open(!) And who's shots were more consistently in focus? Yep, my son's. (BTW, he stabilized things further in post - it looked great!)

Being a wedding, the soft look of focus hunting allowed them to use many clips that one would discard in a hard-edged piece. Still, it shows that one needs to put in the hours before judging how hard it really is to keep acceptable manual focus under various conditions and for various productions. It also shows that if you have a project to shoot tomorrow morning and you don't have experience pulling manual focus that you shouldn't expect too much and that AF could really help.

FWIW, I have often shot on full frame with a 35/2 or 35/1.4 lens at various apertures on a monopod with follow-focus at tradeshows and I rarely have to dump a shot because of focus issues - and the only time I want an out of focus look is when I purposely twist the lens for a blur transition. If I had AF in those situations, I personally wouldn't bother with it. I want to select the focal point.