dude, the seat tube measurement and approximate height are not sufficient. the standover depends on the bottom bracket height, for instance, which varies frame to frame. and the top tube length is really important for comfort, as well. everyone is shaped differently--I may be your height but have freakishly long legs and a short torso, making me want a taller seat tube and a shorter top tube. Or I could have short legs and long arms--and thus the seat tube would have to be shorter, the top tube longer. Height, in general, matters very little. Many people also like shorter frames, because they're more maneuverable. It's a matter of taste and comfort, neither of which anyone else can help you with.

Again, if you have a bike that fits you well, measure it out and then compare it to the frame you're offered--seat tube, top tube, standover. that will tell you what you need to know and will yield a far better result than asking for people's "experiences...[with] a smaller frame."