So you are a rebel shooter looking to upgrade.....
The 6D has more megapixels than a rebel. We can debate until the cows come home if that is a good thing or not, but the fact remains that more megapixels sell. Look at all the higher end users champing at the bit waiting for Canon to put out a 40+ Megapixel camera..... kind of proves the point.
GPS. Some regard it as useless, some as nice to have.... fact is that the "toy" point and shoots have it, and if you are trying to entice them up to a bigger and better camera, features like that help.
ISO range. The ISO range beats the c**P out of anything in the rebel line. It will be interesting to see what the image quality is, but with a lower pixel density than APS-C and using the latest technology, one would expect to see image quality almost as good as a 5D III.
Focusing. This is aimed at people upgrading from a rebel.... one would expect that the focusing would be better than a rebel. Canon certainly isn't going to make it worse. The low light sensitivity is the best of any DSLR out there.... period! Rather than focus on how many points and what type they are, wait until the camera is reviewed by independant sources..... anything said now is speculation. All that can be safely said is that it SHOULD be better than a rebel and SHOULD be worse than a 5D III. And they have included AFMA that is lens serial number specific and at both ends of a zoom, yet another feature rebel shooters do not have.
The viewfinder.... OK, it's not 100%, but it is way better than on a rebel.
The camera has HDR and multiple exposure modes.... sorry rebel....
63 zone metering... sorry rebel....
I would have liked to have seen the articulated touchscreen of the T4i, but the addition of WiFi brings up the potential for a phone or even Ipad to become the touchscreen and who cares about articulated when you have removable? WiFi is so much more than downloading images. This is a function that has the potential to change the way a lot of people interact with thier cameras. Time will tell how it is implemented, but there is a lot of promise here... and by the way, it is yet another feature to entice rebel shoters to upgrade.
Movie modes....I would have liked to have seen 1920 at 60 hz, but I can understand why it would be left off.
Is it better than a 5D III? Of course not. Is it better than a rebel? Of course so. And it's priced in the middle....
If I were shooting with a rebel and wanted to move up to something better, this is a good place to go.