I consider what the bike is intended to do, and how the ride compares to other bikes I've ridden that were built to do the same thing. An example is, my judgment of a nice riding crit bike will be completely different than a century bike. The crit bike might ride like crap on a century, and the century bike will have issues spinning up after the turns and probably wouldn't want to be pushed through corners.
Knowing what a bike should feel like will ultimately result in more bikes. Then, you'll undoubtedly want a nice all rounder...