First, save the "i dont need gps," or the "if you have gps you will die" comments,
What do you need a GPS for? I drove for 40 years without one... besides, theyíre dangerous...
I picked up a Garmin Nuvi (an older model, 250 I think) a couple of years ago and I love it! Itís not waterproof (I usually donít opt to ride in the rain and if I do get caught..., I just put a baggie over it or put it in my pocket) but they have some even better reasonably priced units now that are waterproof. Check out their 500 series ($200 on Amazon). I havenít read up on them in depth but at a glance they look really nice!
From the research I did before I bought mine and from my personal experience with it, I think Garmin is the hot lick. Great maps, satellite acquisition, fast processors, feature rich, intuitive & easy to use software, ...
Iíve had no problems with vibration, even on my terribly buzzy V (yup, kidding again) but I would read the reviews and be sure you get something with a bright display. A unit that may be fine in the semi-shade on a carís dashboard might well be impossible to read in direct sunlight.
Iíd love to have the additional functionality of a Zumo 550 but I thereís no way Iím going to invest that much in a unit until I can get one with real-time weather maps.