Be wary of the Zumo 450.  It works great, but you're probably going to need to fork out over $100 more to get it to work the way you'll probably want it to work.

$5:  Although it comes with a motorcycle mounting kit, you'll be surprised to learn that it does not include a speaker.  (The specs say "internal speaker"... go figure)  You'll have to go buy either a headset, or a patch cord to run to your stereo. 

$10:  The 12v wiring harness (that comes with it) does not include the standard male end of a lighter.  So, if you're like me, and you want to run it to a cigarette lighter, you'll need to go purchase that connector, and wire it yourself.

$80:  If you want to move it between your car and motorcycle, you'll need to purchase the windshield suction mount.  The good news is that this comes with a speaker.   But, like the bike kit, the sound won't work unless you run your 12v power to it.  Which brings up the next piece of bad news....

$25:  The lighter connector, that you just made for the bike, won't work in the car.  The plug that goes into the car mount is a different connector than the plug on the motorcycle mount.  So, you'll have to order the Garmin 12v cigarette lighter power cord....which, of course, won't work on your motorcycle (a different connector, if you're keeping up).