something2say, hahaaa bless you - well at least you recognise the things in my above message happening to some extent. Awareness helps at least a bit, much better than finding out for yourself anyway.
Not all first dates are terrible, not all first dates present you with someone you barely 'recognise' from how you get on, online and on the phone etc (and sometimes even physically despite swapping pics)
BUT - I've been on many, many dates and have been amazed time and time again by meetings that seemed destined for great things going by the excellent online and phone contact, that in reality have no spark, no conversation, sat opposite someone who looks nothing like their pictures - like snapes date recently where he managed to disguise having no teeth in pics, but not in real life....
I've also had the above happen a few times where we have got on so well that I dropped other people I was talking to, so by the time the first date goes so unexpectedly badly, you have to start all over again and the other ones you were talking to have copped off and left the site or think you are a flaky twat for letting contact between you vanish.
So for that reason I find it best to meet in real life asap, commit to as little time as possible, have an excuse ready to get away (meeting friends/family etc) and THEN once that bit has gone well, and another date is agreed, THEN you can get a smidge more excited - and definitely do not have all eggs in one basket.
Like I say my worse case scenario thing doesn't always happen, but it is is very likely. Too likely not to have your 'safety' measure in place just in case (meet quickly, short initial date, multi - date)