if anyone of you have ever ridden/picked up a really NICE mixte or ladies frame, then you'll soon notice that they are not all tanks. it just so happens that most of the ladies frames you see are bombproof schwins, busted bike boom era peugots, etc. etc. i used to have a jack taylor ladies frame that was probably the finest fillet brazed bike i've ever seen. set up as a single speed w/ horizontal dropouts. light as a feather, but way too short for me to comment on ride handling.
also, please note the difference between mixte and ladies frames. mixtes have another set of stays that run between seat and chain, dividing the typical rear triangle into 2 rear triangles. interestingly enough, several french frame builders and some more recent japanese (and a few american!) are designing mixtes for heavy, heavy loaded self-contained touring under the assumption that they distribute weight better than traditional top-tube bikes. such as this colin laing mixte which i'm sure some of you saw on flea-bay a few months ago:
not exactly single speed/fixed, but certainly cool. wrt the terry frames, my former roommate (lady, approx 5'3ish) has a lugged steel terry that she's ridden for almost 5 years including 4, or perhaps 5, serious tours. a really nice bike.