No doubt the Zumo 550 is a good unit, I believe it is the same as the HD unit. I have the Nuve 350 about the same features, but not made for motorcycles.
I am sure the Zumo is more vibration resistant and water resistant, where as the Nuve does not make that claim.
The Zumo 550, is seven hundred buck or so the Nuve is 250, 300.
I keep a zip bag in my pocket in case it rains, or just pull if off.
I also have a old Garmin legend, it never leaves my bike, I mentioned before it's old and hard to get it to come on, so it never gets turned off.
These are cheap now, I think you can get them for just over a hundred.
They are basic, units hand held, water resistant.
Small screen NO find gas stations motels.
One thing I do like it has a tracking feature, that show where you came from. Very nice to retrace your steps when you get lost.
When I go any place I use both. Each one has features that I like, and I keep them doing different things.
If you get one, get a mount for it.
Ram make several
http://www.gpscity.com/ramb238
Try to not look at it while you are going down the road but I do every once in a while and as long as you are careful you are ok.
Don’t do it in traffic, on turns.
Even if you don’t look at it while you are going, it is great to pull off and have the GPS right in front of you already turned on and the satellites already found.
When I am touring I also keep my map right on my windshield. I have suction cup with little clips like you use on the refrig, and fold my map up and stick it right on the inside. I also keep a marking pen clipped to the map.
It is a real nuisance pulling off the road getting out the map, GPS and finding where you are. With this set up you are off the road and back on in thirty seconds, usually turning around right after that;-)
Oh yea, one more thing I know alot of people who carry grease pens, and write the road # on the windshield. When they are home, motel they just windex them off.
I just write the road # on the map in large letters so I can see them.
Aftermarket GPS 
Agree 
Linear Mode
