The video resolution improvements, death of moire and aliasing especially, this all sounds great. I suspect we'll get a "EOSHD Canon 5D MkIII Shooter's Guide" pretty soon :-)
Two things I'm looking forward to find out is how well it handles low-light, high-iso (over 1600) compared to the existing DSLRs (and the GH2) and very important, what the price will be here in Europe.