Well, I live in the affluent north shore suburbs of Chicago and there are Birkins on the arms of ladies in the grocery and drug stores here...Last weekend there was a baby-toting, camaflouge (Da Nang?)wearing Mom carrying baby in one arm, 35 cm black Birkin in another. She sat down at the Corner Bakery and pulled a ziploc of baby treats/finger food from her bag!
Last summer I complimented one woman (stunning, she was) with a camel colored (slightly lighter than 'gold'??) Birkin 35cm - while she and I were waiting to cross a street. I told her she looked amazing and her bag was very, very nice.
She was so geniunely happy to hear it - she melted and smiled...it was nice. I don't know if she knew that I knew about her bag.
Since I had only said it was 'nice'...oh well. Maybe that was best.
However, I'm definately a hypocrite a bit on this ....so to answer the OPs OTHER question....if she tries to sign up a new client with Birkin in tow, what kind of impression would it make? I say - Be Careful!
I agree with another poster's point that while truely upper class wealthy people are so secure in their fortunes that they will be made to feel more comfortable with their agent's good taste and good fortune the EXACT OPPOSITE feeling can come from the ambitious upper middle class. They can be jealous and 'put off' by the uppity-ness of a Birkin totin' real estate agent. It may not work to your benefit! You have to decide: do you deal with the truely intergenerational wealthy? or the double income $250-$350K crowd with car payments and vacations on credit cards?
Frankly if you're in a midwestern college town I'd be careful not to wear it all the time. If it's A2 (ann arbor) use it in A2 Hills and the three other suburbs that have old money. If you're in Columbus, OH or Bloomington IN or East Lansing, forget it!