As someone who does seo, a sitethat could objectively rate the available tools would be fantastic.
However, I think it would prove difficult to have all the elite players (Bruce Clay, SEOmoz.org, etc) agreeing to the standards of the reviews since each piece of software measures different components and each calculate values with different elements.
But if I came to that site if I didn't find the top players known in the field and only saw the likes of SEOelite and aeiou.com, it wouldn't carry much weight.
From a pure domaining perspective, I think the domain right now is prolly worth around $60 - if can develop it with all the elements I mentioned, then you're taking that site to an entirely different level.
Just my $.02