So I've taken up road cycling in the past several months since March after not using a bike for almost 5 years and have slowly worked my way to doing about 125-150 miles a week over the summer. I'm currently on an old schwinn (70's) which really isn't cutting it for long distances so, I've been looking pretty seriously at getting a new bike the past few weeks before the 2011's roll in. Most of my test rides I've been doing on 54's or 56's depending on the brand but when I went to go try out a Felt F5 the other day the guy threw me on a 52. Oddly enough after putting about 5-6 miles on it in a test ride it seemed like it fit really well. I'm 5'10" with a 31.5" inseam so in theory I should be on a larger bike, right? I was just curious if there was anything different about more aggressive geometries fitting better in different sizes than standard fits. I may be over thinking it a bit but I just wanted to get some feedback on why I'd be moved from a 54/56 down to a 52 with a switch from a Trek Madonne 4.5 and a Giant Defy Advanced 3 to a Felt F5. If it feels right should I go with it or stick with something closer to the recommended size.

TL;DR

Is a 52 too small for someone 5'10" with a 31.5" inseam if the bike shop is recommending it?