"...the reality of unfriendly locals and scruffy streets..." - sooo many people warnged me about the arrogant Parisians, funnily enough, very few of them had actually been to Paris We found the locals to be fantastic - as long as you tried to communicate in French first, they were always happy to help out. Actually, I was in the Louvre doing an audio tour of French sculpture (highly recommened, by the way), and a lady approached me and said "is your aduio tour working?" - in English! I thought "how rude" - she's in a foreign country and just assumed that I spoke her language She could have, at least, learned how to ask if I knew English...
Anyway - in summary, I found Parisians to be just as friendly as anywhere else I've been, so don't fall for the stories about their poor attitudes. Sure, some people may have had bad experieces, but I've found in my world travels that your experience is usually far more dependant on your attitude than anyone else's...