The Canon 5D series is pretty much the top of the line Canon DSLR unless you're shooting professional action sports on the regular (Canon 1D for that). I've extensively (and still do) use the MKII version. It's been my workhorse for over 5 years now. I've used this one, the MKIII, on a couple of occasions and it is well worth the money and upgrade from the MKII. The slow motion video capabilities are rad. Have gotten some really good footage with it so far. Higher megapixels for photo are also a great reason to upgrade. Personally, I would buy the body only as I have all of the lenses I need, including the 24-105 that this kit comes with.
If you don't have a real need for full-frame, you aren't shooting pro or semi-pro video, then this is not the camera for you. Take a look at the 7D or even the Rebel series, they're far cheaper and can do just about anything the average photo-enthusiast would need.