I occasionally ride the early 80's Univega Mixte I built up for my wife and have ridden 3 or 4 others that have past through my hands.

I like them and am well past giving a care if others think they are only a ladie's style frame. If it works for you go for it.
Also with the aging of the American population frames that are easy to step thru to mount seem to be becoming more popular. Advancing years can make it harder for some to lift their leg high enough to mount a diamond frame bike.
I see quite a few 'step thru' syle bikes a my LBS.

Like WNG said the mixte's were designed as a Unisex frame.

http://en.wikipedia.org/wiki/Mixte#Mixte

See Wikipedia definition:
"Mixte" (pronounced [mikst]) is a direct appropriation of the French word meaning "mixed" or "unisex". The usual North American bicycle industry pronunciation of this loan word is /ˈmɪkstiː/.[8]