I'm 5'8" with a 30" inseam and I recently decided on a 54". It has a snug standover and lower seatpost exposure, but so does my current steel road bike that also has a 54.5 ETT and I've always liked the feel of it. I test rode the CAAD 52 and the 54 and other than standover, I could not tell the difference in fit. I liked the bumblebee color of the 54, so I went with it.