Can't tell from the NDS photo, but are we talking about the basic, largely plastic Simplex derailleurs here, or no? Those can present a bit of a durability issue, I gather.

I don't know my Peugeot models, so I'm not sure what you'd expect on there. I do know that my girlfriend had a similar bike to the one you've posted (hers pulled out of a relative's shed), and considered it a perfectly good ride (not raving, but no complaints). I also know that UO8s I see around where I'm living these days (lots of Peugeots in Quebec!) either look like they could use an upgrade in the derailleur department, or already sport replacements (like my girlfriend's follow-up bike after the above-mentioned mixte bit the dust - a UO8 with a nice, somewhat newer Deore RD in back to keep things running smoothly).

Generally speaking, it is my impression that mixtes are popular these days as good utility riders for the right person, and that they have a bit of 'camp' value. I've certainly heard the term 'cute' a few times from female acquaintances. It is relatively unusual to see a particularly well-appointed example (one built with a top-tier tube set, say, or kitted out with higher-end components), though they are most definitely around. See the thread posted recently about this Nishiki mixte with 26" wheels, for one nice example - or take my word on the Cromor Marinoni I recently spotted in a shop window here in Montreal. I don't tend to "sneer at" mixtes, necessarily - since relatively few are particularly well-appointed, I find the nice ones really stand out for me.