After owning various Nuvi units (wife had a 200, I had a 260) AND a Zumo 550 on the bike, I can say without a doubt I prefer the Zumo on the bike and the Nuvi's in the cars. Wife just traded her Zumo 550 to a friend of mine for a new 265WT. He wanted the Zumo for his new Ultra, and she wanted to get back to the Nuvi form factor.

I just bought a Nuvi 760 for my car so I don't have to transfer the Zumo back/forth anymore.

Not sure about the Zumo 660 since they don't come out till April. I'll have a look/see at one in person once they're available. I do like the form factor of the Nuvi's over the Zumo 450/550, and if the 660 retains the viewability in direct sunlight like the current Zumo models, I may get one to try out.

 

Walmart has the Nuvi 760 for ~$220 (online purchase only). I jumped on one when I saw them at that price.

Audio out, FM Transmitter (so you don't HAVE to use the 3.5mm audio out port), Bluetooth, SD card slot, etc.

 

That's a good price. I wanted something waterproof though, like the Nuvi 550.