Same as Stargazer, I haven't had many surprises. I've only had one person be significantly larger than they "led on" with their pictures, but she told me in messages beforehand that she was large, so she still wasn't deceptive.
I've been on lots of dates through online dating though, and a significantly smaller number of second dates, so obviously I can't tell if there will be chemistry and all that, and there are plenty of little things that are near impossible to convey online that you just have to meet the person to discover. But I don't think I've ever gone on a date and thought "wow, you are nothing like what I expected!".