I bought the Nuvi 760 for use on both of my bikes and it works perfectly. I now have about 10k miles using it and I have had NO issues involving vibration. I put an 8gig card in it and loaded enough music to ride from AZ to NY and back and probably never hear the same song twice if desired. I run a Magellan Meridian Color on my ATV's and have flipped them twice and ride them hard and vibration has never hurt the GPS.
Facts:
1) The Nuvi models are not waterproof so don't go scuba-diving with it. If you hit a hard rain, place it in your pocket until it stops. (Time involved = 3 seconds; inconvenience = zero)
The Nuvi 500 series IS waterproof
2) The Nuvi has a larger and higher pixel screen for better viewing.
276 series has a higher resolution display and uses it better and it is more readable in direct sunlight
3) The Nuvi will allow you to receive and MAKE calls through your Bluetooth phone. The Zumo won't.
Wrong. PLUS Zumo has a bluetooth host channel
4) The Nuvi is half the cost or more of the Zumo
Not necessarily
5) The Nuvi has about a 5 hour battery life, but who cares, plug it in to the receptacle making battery life a mute point.
Zumo's battery life is like 4 hours, the 276 is like 16 - sometimes you don't have an outlet - more often you don't have an AC adapter.
6) I wear gloves and using the touch screen on the Nuvi is extremely simple.
Zumo does touchscreens with gloves better than Nuvi - I prefer buttons. 276 wins.
7) The Nuvi has many more features.
Not really - except for MSN direct support and Audible Books and the travel guide which no one that I know uses, there isn't anything significant to distiinguish Nuvi.
No. Wait!! That's right. Zumo can disable autozoom. Nuvi does not.
8) Both the Nuvi and the Zumo mounts very easily by using the RAM mounting system. I utilize the Stem mount on my FJR.
Zumo and 276 have more secure mounts
9) The ONLY advantage of the Zumo is the water-proof feature. But for the additional cost, you can buy two Nuvi 760's and still have money left over for other stuff.
Not true. It is also vibration resistant - YOU may not have had issues, but parts WILL eventually shake free of the board if you try hard enough.
Summary: Garmin stresses the water-proof and vibration features just to get that extra $300-$500 bucks from you. It's like paying $9 bucks a quart for so-called 4-stroke motorcycle oil when paying less than $9 bucks a gallon for Rotella T diesel oil is as good or probably better for your motorcycle.
If you buy a Nuvi, then extra cables, brackets and such, you will have dissipated some of your financial and convenience advatages. In any case, the hardware is a one-time investment and the price spread need not be the list price differential. I don't believe that Zumo is the perfect answer and I've had most of them. But YOUR experience may be different.