Yeah, I'm 5'10" and I take a 57, while lots of guys my height are on something a bit smaller... it varies. The thing is, seat tube length be damned; that's only about standover clearance. The real variable that matters (along with angles) is effective (horizontal) top tube length. I wish framebuilders would start sizing using that measure... (My bike is 57 square, BTW).

My rule is if you're in the fat part of the bell curve and don't have any issues, you're prolly best off with whatever size you're most comfortable on using a 120mm stem. Make that up to 135mm if you have freakishly long arms, or maybe as short as 90mm if you have a bad back or whatever. I guess 105-110mm might be more optimal for most women, since they have proportionally shorter forearms.