Not that it's a huge deal, but AMD is releasing their own true HD 7990 soon. Could be the end of this month at the soonest, but before july for sure.
Their partners have full permission to change anything they like, so you may even expect a liquid cooled version someday.
The bad news for Asus is this GPU is expected to be at least very close to as fast as the Ares II, and definitely faster than any other "7990" for sale today. The GPU uses 2 of the Tahiti XT2 GPU chips, which are the ones found on the 7970 GHz Edition. Final clocks haven't been released, but all the other specs are basically the same as every other 7990.
Edit: Oh yeah, they're releasing a 7790 soon too. Expected to be ~10% slower than a 7850.