GPS for bicycle?

Hello,

Can anbody recommend a GPS for use on a bicycle?

At the moment I have a Magellan Meridian Gold with Directroute
autorouting but have some problems:
- autorouting is very limited. It always seems to calculate the
"quickest" driving route and not the shortest route
- autorouting seems to be very slow. I suppose because it wasn't
designed for this at the outset
- after a few years I feel it's time for some colour

I'm thinking of either a Garmin Quest or a TomTom Rider (when it
eventually comes out). The only drawbacks I can see being of
dependency on Li-Ion batteries.

Does anyone have any better suggestions?
What is autorouting like on vehicle-specific models? Is it faster than
on my Meridian? Can you configure them to build a shortest route,
instead of the fastest route?

Thank you!
Taka
.