My friend went out with a guy on a couple of dates, he was 7ft1 and she is 5ft5, he was just too tall. Nice guy but she couldnt cope with everyone staring at them wherever she went.
I'm 5'6 (and a little bit.... what?? It counts!) and once dated a guy who was 6'7. We lasted a whole two weeks! (Less to do with height difference and more to do with his w@nkerish tendencies to be honest... Tho I did get neck ache a couple of times).
My friends Janet and Dave are 5' and 6'6''. Highlight of their wedding was the photograph where she stood on the steps about four up from him to be around the same height.