I got my 7790 today. It's the real deal, the numbers from tom's are legit.
This is pure stock just using the same settings I used on my old 5830 card, it's probably possible to increase significantly with optimizations and overclocking-
Note that cgminer didn't get close to these results, might be some bug involved or a setting I needed to use.
Power usage, measured from the wall, increases by about 38W while mining.
In my crowded Dell XPS 8500 case, it's running at a cool 58C at full load with no increased fan settings.
For comparison purposes, my old 5830 ran at 70C, did about the same or slightly less MH/sec (stock, I know I could have done more with overclocking), and used about 110W at full load. Next gen AMD cards are awesome miners, it's just too bad that the time of ASIC is almost upon us.
I'll do some additional testing and see how it does overclocked, since it's running so cool and using such little power I'd be shocked if I couldn't get some more hashing out of it.
FYI, initial test at mining litecoin was a total failure, seeing like 7kh/sec, obviously my configuration is all wrong but I'm not sure how to optimize it.