I just picked up a
Garmin Zumo 550 from
http://www.pcnation.com for $627.15. They'll ship free via Fed-Ex 3 day...but DHL overnight was only $11.45...so I figured what the heck. Like the TomTom Riders, it was designed for motorcycle use, vibration and water resistant, and easy to use with gloves. It includes car mount, RAM mount, latest version of Mapsource dvd and has a few more features over the TomTom that appealed to me. Some don't care about those features. I did.
For those that don't, there are even cheaper models (such as the Garmin 26xx, 27xx, and 28xx units for about $200-300 that are also waterproof...but you gotta buy the bike mount separate).