We have a Garmin Nuvi 1450LMT. It is pretty basic, I have it on Ram mounts and powered by the 12v power port in the right pocket. It has not bluetooth, doesn't play music, it show pictures but I don't have any, and it has an internal speaker so it doesn't connect to the bike intercom. I personally don't like the voice guidance and even when I use it in the car I turn down the voice. It's not waterproof, but I put a zip lock bag over it in the rtain and haven't has any problems.
What it does have is a 5" screen that is very easy to read in any light. The guidance has been very good, It will show the correct lane to be in and show a visual representation of the interchange and signage of upcoming turns. There is a traffic function and the ability, if you set it, of routing around traffic. It also has lifetime maps and traffic. The maps can be updated 4 times a year, and if I lived where there actually was traffic I would find the innformation and the ability route around traffic useful. It has saved me time in riding through cities, and the maps and basic (upgradeable) traffic came with the price of the unit, a BlackFriday Doorbuster in 2011 at Target.
Garmin says it is $315, Black friday deal was $159, got $10 off for using a Target card and a $10 gift card for some reason. Total cost was $139.00. Well worth the money.