I have a planetbike 9.0 bike computer from REI.
I like to keep watch of my trip time, speed, average speed, and check the temp. Waterproof is great as I'll ride in any weather (no car haha).
I also have a suunto core watch that I can keep an eye on the altitude and barometrics around (although i often glance up at the sky and take notice of the winds).
I really like the easy to read screen and the ability to just pop it off and put it in my pocket. Not having a light isn't a problem since when I'm riding in the dark I'm keeping my eyes out for possums and critters more so than my speed. Cheers!