In many ways, it's actually better cycling in dense urban traffic moving at a snail's pace than say, a 5 lane road (2 in each direction, shared center turn) of the sort that are arterials in suburbs or might find near your local mall when traffic is moving at 35mph.

Source: I've put about 14,000 miles on a bicycle, half touring, half commuting in Cleveland and Boston. for context, that'll seem absurdly large to non-cyclists, and quite small to serious cyclists.