I'm thinking about getting a cross bike for commuting since my single speed mountain bike is a bit unwieldy and I was looking at the Cross Check since I can get the frameset from aebike at a good price. The only thing that I am unsure of is the sizing. My roadie (Specialized Allez) is a 52cm, but from what I've managed to glean from the forums, cross bikes run large. Is this correct? Does that mean that I should invest in a 50cm frame? I've looked at the geometries online, but since I am unsure where each company measures from, conversion from mm to cm is hard, etc, I'd rather ask then get the frame and have to try to sell it. I was also interested in the Soma double check, but I'm not sure I can justify the extra price just because I think blue is purdy...
Oh, and I promise to never, ever refer to myself as someone who does cyclocross. I will "commute using my cyclocross bike."
I am 5'6" and ride a 52cm Trek 5200 carbon road bike. I was in the same position as you, and bought a Surly CrossCheck frame sight-unseen. My frame choice was based on comparing my road bike geometry to the geometry listed on Surly's website. I ended up with a 46cm cross check frame and it fits me perfectly. I have an ultegra triple group on mine, with Avid Shorty brakes, eggbeater pedals, and Bontrager Extralight wheels. It weighs in at just under 20# and makes a great road training and touring bike. You need to look at the standover height, and most importantly, the EFFECTIVE top tube length (the frame has a sloping top tube) when comparing to your road bike. It is easy to end up with a cyclocross-style frame that is too high and too long.
Huh. Interesting, I never thought I'd have to drop to a 46cm! I'm also 5'6" so we're probably similar - although I imagine if you are male then my legs are a bit longer (short torso, long legs, yippee female anatomy!).
I plan on building this one up as a single speed to start since I'm a student and less parts = cheaper. My biggest concern will be putting on bomb-proof wheels since the potholes in Boston can eat you if you are not careful. It's also why I have emergency flares, in case I fall in and cannot get out.