i've got a garmin streetpilot III on my bike and it's pretty cool. i'm always a bit paranoid about getting lost, so it's nice to have. but the cool part is that i can route out a ride at home on my computer and it will direct me while i'm on the road. i use a ram mount on my tubular handlebar, so it should work just as well for you guys.
garmin intro'ed a new high end model with a touchscreen to replace the spIII. but they also introduced a palm pda with all the functions of the spIII for a lot less money. plus the processor is faster and the screen is better. i'm thinking about picking one of those up.