I just finished building up a road bike and included an Ergobrain 10. It is a little slicker than the Cateyes I've used previously, though obviously pricier too.
If you install the cadence sensor, it automatically determines which cassette you're using. There are buttons built into the ergolevers that control all the computer functions, which is pretty cool. The display shows you which ring and which cog position you're in, as well as the number of teeth for each, and the computer has a comprehensive set of training/interval timers with, e.g., audible alerts when you've completed an interval. The interface is a little complex, but once you figure it out (i.e. read the manual five times), it works pretty well. There's a backlight too, which is useful on the trainer.