I think a lot of it depends on the particular panel you end up getting. My friend and I just bought identical i7 high-res anti-glare 15" notebooks, and my screen is easily twice as bright as his. (our panel P/Ns are even the same)
In my past experiences, the 2008/9 unibody 17" screens are the brightest and I'd say the new 15" AG screens are the brightest of the current lineup. Again though.. I think a lot of it depends on the actual panel you end up getting.