I love threads like this because I am constantly wrestling with whether to go get a purpose built motorcycle GPS unit or improvise with other devices and technology. I used to have the ZUMO 450 but gradually grew tired of the constant updating and storage capacity issues. There is nothing very intuitive or user-friendly about the older ZUMO devices in my opinion. Maybe the newer ones are better but the prices are absurd.
This year I'm going to see if the smart phone or tablet methodology works.
Here's an article I'm just now reading lately.
https://www.webbikeworld.com/gps/nexus-7-gps/using-a-tablet-as-a-gps.htm
Garmin prices were always "absurd". I have several 2720s, the box of one of them still carries the original price of $750. That would be the one I bought on Amazon as "used". It arrived looking like it had never been taken out of the box, and it was $58!
I just bought a second Nuvi 765T, again on Amazon and again in "As New" condition, for $60. It had 2010 maps installed and cost me $45 to update to 2015.
The update process did not go well, and involved spending 90 mins on the phone with Garmin tech, and the sending of a bunch of log files. Turns out the issue was that the latest version of Garmin Express was broken, preventing the unit updating. Boos to Garmin for that, and Cheers to Garmin for spending so much time patiently fixing what is now an obsolete unit.
The 765T is the Nuvi that most closely replicates the entire functionality of the Zumo 550. The only real difference is that it does not have a Headset Profile in bluetooth, which is annoying if you want it to handle the phone on a motorcycle (it won't).
My current 765T has been on the bike for the last 40000 miles and performed flawlessly, so replacing it with a new unit for $105 was a no-brainer really. The old one is just beginning to show its age and I'll keep it in the topcase as a spare.
I'd love to buy a Zumo, but not at any price. My set up while riding is a Nuvi 765T and a StreetPilot 2720, total cost was around $165 and I've never had cause to regret those purchases.
I am very interested in the new Garmin Dezl 770. It is the first "non-Zumo" unit that Garmin has allowed a Headset Profile. It is $400. The main issue is that it is a 7" screen, and that's too big. The Dezl 570 (5") doesn't have the Headset Profile. When the price of the 770 drops a bit I might jump in, it is at least $300 cheaper than the Zumo, and I'm not paying that for waterproofing, a slightly brighter screen and vibration proofing, whatever that means.
I've never had an issue with vibration, and the Nuvis, and baggies remain waterproof.