It is the minimum that Canon had to do to not lose significant market share to Nikon. They had to improve auto-focus and exposure metering, and it looks like they have. They needed to improve low light performance, and it looks like they may have done enough to close the gap with Nikon. I think keeping the 5D Mk II in production at a lower price point is an interesting move, and may hurt Nikon more than the Mk III will. In the end, the competition between Nikon and Canon is making things better for DSLR enthusiasts.
If I were a pro or more into shooting video, I might feel like I have to upgrade. However, this cost conscious amateur will probably pass on the Mk III. I (and not my camera body) am still the weakest link when I fail to capture a useful image. I still have some use cases where I don't really have the lens to get a better result. Thus, I will focus on lenses for the next year or two, and start saving for the 5D Mk IV.
For a light body pro DSLR? YES! I was disappointed with the Mark II in the aspect that the burst rate was soooo slow. The video quality on the Mark II made up for it but if you enjoy shooting sports you only had two options spend another 2 grand or buy a APS-C sensor. The Mark III looks promising for it's price range to performance.
So far, so good. I thought it would be kind of the same, just with better low light. But it feels better, more responsive, improved controls, amazing (and a bit daunting) autofocus that does clever things like change focus point with camera orientation. I have a MkII, I was expecting less from Mark III (bought it for ISO only, really, would never consider NIkon given my investment in lenses) than I got.
It sure is. I've been waiting 2 years for this camera. I preordered it the morning of the announcement.