I am using 7D and T2i. I guess the primary reason I use MPSC is that I find it much faster than compressor and haven’t really run into any problems with it yet. When batch converting hundreds of clips I find the same it saves to be substantial.
Why ProRes HQ? That seems like overkill to me. I have been using ProRess standard and LT and it seems to work fine.
As for sound I use a Zoom H4N and haven’t had any sync issues – although the clips aren’t very long – (and can’t be more than 12 minutes due to the restrictions of the camera) so it is hard to tell what would happen on an extended clip.