I'm relatively new to cycling--2 1/2 years. It has taken me 5 bikes to get the one that fits.
First...Scott Contessa Sport 52cm--Really cute and fast, but too small.

Second...Jamis Coda Comp 54cm--works as an all around beat about Houston bike.

Third...Bianchi Avenue--Too heavy, too slow, no fun...thought it would work as quick errands bike, but frustrating to go so slow.

Fourth...Jamis Xenith Comp 54cm--too big--reach too long among a host of other problems, too light (lots of lateral movement in slightest wind... scary for me to ride down hills because it feels like I'll be blown off). Really a fast bike though, and if it fit I'd try to become accustomed to the scary movement. I should have ridden it longer and in tougher conditions. Also, given that I always moved back on the saddle on the Scott--sort of hanging off the back, I thought that sliding forward on this Jamis was better...NOT!

Fifth..Cannondale Synapse Carbon 5 T--Practically perfect in every way! 50cm--great fit, no pain anywhere and I can now actually sit on my saddle without sliding forward or pushing all the way to the back! I didn't know that folk could actually sit still on their bikes! No blowing in the wind. Now, I love going up and down hills--before my Synapse I only wanted to climb not descend.

With each purchase the different shops were as helpful as they could be given my limited experience in articulating exactly what I wanted and how the bikes that I already had made feel. Still, I wish that I could have found the Cannondale first. I do ride the Jamis Coda Comp a lot. It's great for commuting and somehow it fits in a 54cm, while the Xenith in the same size doesn't. The other three bikes have become wall art for my garage.