I'm 5'9" and ride a Cannondale CAAD9. My dh and LBS basically picked my bike for me, cause I had no clue. It was originally going to be a Ruby, but then they devised a different plan, partially because I'm so tall and don't technically need a WS bike. Dh was upgrading his bike to the Cannondale System Six, but already had very nice components on his CAAD8, including DuraAce. Our LBS was able to get us a screamin' deal on a CAAD9 frame and they put all dh's components on it. I ended up with an extremely nice bike, lighter with better components than I would have gotten. I have two friends who are about 5'6", who have the Ruby and love it.

One difference I ended up making recently, that didn't work for me as a woman, was changing the handlebars. I was never comfortable in the drops before and finally switched to smaller, compact handlebars and it made a huge difference. I use my drops all the time now and can brake and shift fine. My handlebars aren't called women specific. They are just called compact or something, for "people" with smaller framed bodies, whether a small man or a woman.