Before you walk into a bike shop and look for your new dream ride for next season, consider this; there is no easier way to be deceived by a bike than to judge it from just a test ride.
A short ride on the bike will not give you the same information as a long training ride for obvious reasons.
Unanimously the most important factor in choosing a new bike is making sure it is the right ‘fit’ for you. One option is to get your stack and reach data from a fit on an adjustable rig or your old bike, and from that you can start to narrow down your selection.
Slowtwitch.com have a comprehensive list of stack and reach data at http://www.slowtwitch.com/stackreach/index.php
Another option is to use Frame Finder in conjunction with your Certified Retül Fitter.
Then you can start test riding different bikes. However you want to standardize the components and wheel sets. The reasons being that differences in these can significantly alter the feel of the ride. Lower tyre pressures and softer more supple tyres will feel smooth and great, whereas higher psi’s and more robust tyres will be harsher but more responsive. Is the stock saddle correct for you anatomy? Do the bars match your anatomy? Is the drive chain well tuned? A well tuned bike will give a better impression than an out of tune bike.
So once you’ve standardized a selection of bikes which suit you from your stack and reach data ask the shop to set those bikes to your fit data with the same wheelset to neutralize the difference between tyres.
This process will ensure you spend your hard earned cash wisely and provide you with a steed which will help you achieve your performance goals in comfort and with reduced injury risk.