The 5D Mark III is better than the Mark II, no doubt about that. That being said, I still have some reservations because of the big price difference between the two. I'm not convinced it's necessarily worth the ~$1500 more than the 5D Mark II, unless you are getting paid for your photography, or if you need the advantages/features it provides.
There is no harm in holding one in your hand at your local shop and playing with it there.
Currently for sale: N/A