PARIS; what's your favorite neightborhood/arrondissement and why?

[M.Kaplan]

Warren,
I think this thread covers it pretty well. The OP was about bistros, but the same applies to interesting neighborhoods in which to stay. equally.

Best Area in Paris for Bistros

My wife and I are going to Paris in the fall. We will probably stay in the 9th at the hotel de Nell. Is this an area where decent bistros will be within walking distance? We really would like to stick to proper French food while in Paris. All suggestions will be appreciated.