The craze doesn't seem to have abated yet. About 1/4 of bikes were fixies, more in outer areas. The most sawn-off bars I saw were about 10" wide, which must have made handling "interesting". Lots of slack chains. One change from a few years ago is that most people use lights after dark now.
Off-topic, I saw two peculiar belt-drive folders with small wheels around Piccadilly Circus - what are they?