I have the eTrex Vista, I think it's a couple of hundred bucks these days. 24mb of RAM, can hold the complete street maps for MD, VA, DC, parts of PA, NY, and CT. Small, waterproof, long battery life (I use recharchable AA's), mounts easily on the handlebars -- I use a R.A.M. U-bolt mount with their eTrex-specific cradle. You can find that at cyclegadgets.com.
The V is great if you want routing, but I almost never do on a bike (have other things to pay attention to), and it is a bit bigger and uses more power. I just set up the Vista to rotate the map with my heading (puts you at the "bottom" as an arrow pointed up) so I can see what's ahead of me for a few miles. I also use it to backtrack when I'm on a "get lost" ride.
FWIW, both units will provide useful trip stats such as max and average speed.