I agree cadence is an important factor in your performance, but I have personally never felt the need to have it on a cycle computer. I know my own cadence from years of riding, and even as a beginner, all I ever did was count revolutions for 15 seconds and multiply by 4, or if you can get a decent count over 6 seconds, do that and just add a zero after it. As far as a number goes, I've always heard that 90 is a good target, but whether your most efficient cadence zone is right there, or slightly above or below that number, is something that varies with the individual.

For me, I want auto-start and -stop and average speed (a pace arrow is helpful in this regard, too). The other essentials are all pretty much there on any computer - current speed, trip distance, total distance, max speed (not really helpful, but fun) and a clock. My most recent computer is wireless, which I'm liking a lot, too. No ugly wires to mess with.