I used a Mio 168 with Memory Map until last year. It was excellent as the aerial was good so it got a good GPS signal and the screen was perfectly adequate. I used to use it with CoPilot in the car and on the motorcycle, too, with a Brodit mount.
I started using a Windows Mobile powered Samsung Omnia when I started running, to cut the bulk of a mobile and PDA down to just a largish mobile. It's more powerful than the Mio and the screen is a slightly better resolution although smaller. The GPS is buried inside and the trace from a ride through the woods is patchy at best.