I've never found anything wrong with the area between Okubo and ShinOkubo stations (about 0.5km) but the locals consider the area a bit dodgy, maybe because there are too many hostess-style nightclubs around.

The street used to have a lot of 100 Yen shops but they seem to have all vanished except for a Lawson 100. There is a hotel next to Okubo station that has a bunch of floors with a view bar at the top, I forget the name, but maybe that is the one. There are also some nice Oakwood apartments between Okubo and Shinjuku sttion but they may have a minimum one month stay requirement now.