This article was able to get #'s at least as good as the 4890. http://www.techspot.com/article/255-battlefield-bad-company2-performance/page6.html
The launch articles about the 5830 here and at Anands did not show it as well. I believe Hocp got some good #'s out of it as well. IMO, I've been watching prices, the 5830 is not a bad deal for 240.00. VS 210.00 for the ony 4890 available at newegg today. http://www.newegg.com/Product/Product.aspx?Item=N82E16814150438&cm_re=4890-_-14-150-438-_-Product
Bottom line is (money). If you don't have the 30 or 40 extra. You get the 4890, and know you got the fastest gpu from last generation (ATI) !
These two new reviews of the 5830 compare it well to the other 5 series cards in the lineup.
Right in the middle of 5850/5770. IMO , for every reason, everyone and their mother recommends the 5770 over
the 4870, the same applies to the 5830. Which is 60 bucks cheaper than the 5850. ATI needed something in between the
5770~5850, it works for me.