I wouldn't call Sydenham rough at all. Moved to the area about 2 years ago from East Dulwich (just down the road), and I love it.
I guess some might say it looks a bit rough round the edges, and you probably wouldn't fancy walking in to any of the pubs on your own (except maybe the Dolphin), but I have never had any problems, and more to the point, neither has my wife... She did however get some hassle in East Dulwich which is meant to be a really nice area, so there you go.
RE The "fast food junkies heaven" thing, I don't think that's fair. It has 2 kebab shops, a pizza place, a couple of curry houses (one of which is great!),a chinese and a Morleys chicken. There are also a few cafes.
However, to compare to East Dulwich again, Lordship Lane (the high street down there) has about 8 curry houses, 2 chinese, 2 fried chicken shops, 2 kebab shops / late night drinking dens, several cafes and so on, it's not like your average Sydenham resident eats more fast food than people from anywhere else.
I do though
