When I lived in Michigan and mostly rode flats, I loved my 180's. (I'm 6'5" and run 1995 XTR 180mm crank with 46/36/26 rings and an 11-23 cassette.) Living in North Carolina where everything is up-and-down, off-and-on, I want to be able to spin more, and actually prefer the 170mm cranks on my commuter bike. I can't do a Jan Ullrich and push a big gear nearly as easily here.