So anything above a 216 will put you in the top half of testers. Anything above a 237 will put you in the top 16%. Anything above a 258 will put you in the top 2.5%.
I posted the breakdown of percentiles on another message board. Do a search for "Z table" and it should pop up. Or just search for my screen name and look for my posts. Keep in mind that the Z table percentiles I posted are estimates only.
I've heard rumors of someone scoring a 290, but who knows if that is true.
I think the score we get is a raw score. There are 350 questions total with about 50 questions being used for research. So theoretically there is a possible 300 score, but about 5-10 questions are usually omitted because of errors. So realistically 290 is the highest score possible under most circumstances.