i bought one today, i am 5"10 at the moment, maybe a tad under, but am with shoes, and 17, so i may grow a bit more, so i went for the 60cm. it was fitted for me, and the bike had loads of options, including handlebar stem length and rotation. i was fitted correctly, and have long legs and long arms, and feels great on me, 57 was too short for me, i was slightly hunched, though i am finding i am supporting a lot of weight on my arms, perhaps 5-7kg each, don't quote me though, may have just been tired. staff are very helpful and will get you the right size.
edit: they measure your legs relative to the bike, you stand over the bike, not on the saddle, and move over to the handlebars, if there's an inch between your region and the frame, it's a good fit.
