Yes. Quite. The south circular does spoil it somewhat. As does the occasionally slow service. People often talk about the road as if it is an insurmountable obstacle getting in the way of the area's long-foretold gentrification. Not that I think you said this. But I wonder if this is true. There are of course plenty of places in South London with heavy traffic which still manage to keep up appearances. There has to be something worth the upkeep though. It seems to me that the central station area needs a really good rethink because it is such a natural focal point. Not that station redevelopment is always worth it but I think that in this case it really would lift the place if done sensitively.
Something else that seems to signal a more pleasant neighbourhood is a bookshop. Obviously lots of different kinds of people read and I think bookshops actually have a quietly enriching effect on communities. A room without books is like a body without a soul. The same applies to communities in my humble opinion.