i know of people who've been rejected from the top few schools with perfects or upper 900's and decent grades. in one case, it was because the guy had no research experience. i seriously think that if you're applying to top 5 or 6, they weed out everyone who don't have good scores and grades. so out of like 1000 applications, the weeding process weeds out like 500. and then it's research that determines whether you're different than the other 499 people with great grades and scores.
i have a good score, but my grades are crap. no practical research. but, i did take a bunch of grad courses as an undergrad.