GPS technology has moved on quite a bit since I bought my first Garmin III approx 10 years ago!
The Garmin Zumo 550 is specially designed for motos, it has a large bright colour display and many additional functions like a MP3 player and the ability to interface with your cellphone over bluetooth.
The Zumo is quiet pricey compared to similar GPS models just for cars, but I'm definitely glad I went for this unit; its well built and it came with all the necessary hardware to attach it to the bike and a separate mount for use in the car.
It took me around an hour to fit it to my bike, but most of this time was taken trying to figure out how to route the power cable! So I'm all set for a group ride out to the valley on Saturday.