As a videographer - who also dabbles in photography - I am greatly impressed with the new specs of the 5Diii. Definitely Canon's attempt to hold the exact market that I work in. Not the BEST video or photo specs - but damn good ones at that. The price point is slightly higher now than I anticipate it will settle at. Canon's boosting the initial price to get all us camera nerds who satisfy our dopamine addictions through the purchase of new camera gadgets.
Though there are a few minor video complaints such as: no clean hdmi out, no 1080@60fps, and no RAW video, overall this is still a major step forward for Canon. Clean hdmi out (though awesome) I really don't think is necessary in a hybrid camera at this point (but a tip of the hat to the Nikon D800 for achieving this). In a camera at a little less than 1/4 of the price of the C300 I also understand why they won't - even if they could- put in 1080@60fps (something the C300 can't do). Would make the C300 look bad
Though I wish it if this camera did RAW video it would render the C300 moot to many videographers.
Improvements in moire and aliasing will be a major plus. For most people shooting video on their own 5Dii, I think they might as well stick to that camera - remember there is a potential 4K DSLR around the corner
- unless 720@60fps is a necessity to you. The other video improvements - though pretty great - wouldn't be enough for me justifying a jump to the 5Diii (at least at its initial price point).
However those in the same group as me (either having been renting the 5Dii or owning/shooting on Canon's APS-Camera's like the 7D, T2i, etc.) this camera is probably right up your alley. Usually I rent full frames for particular paid gigs but in this case I will be purchasing and holding onto the body for a long time.
There will always be something we WISH a camera had but if we're WISHING it... It doesn't. Get out and shoot with what we have and we'll all become better videographer/photographers.