I have a Street Pilot 2720. As state before it is discontinued so you can probably find them cheap. I use a RAM mount and they are rock solid.
PROS:
Decent size screen. The right side of the screen displays various information (dist to turn, ETA, speed, ETC). It is fully customizable. Large, small, different info when following a route or not,
Auto darkening
Ability save tracks to PC and create routes and send them back to the GPS. Nice for when you find a really nice route to a certain destination.
Weatherproof
Touchscreen works with gloves and 4 side buttons are large.
Ability to mark and name locations (Photo ops, rest stops, etc,) that are not on the maps
CONS:
No internal battery
Speaker is located in the 12v lighter plug (seperate direct wire kit available with audio out)
No auto power off. (I have accidentally left it on and fully drained the battery.
No MP3 or Bluetooth. (28XX series I think have BT)
I never thought I would need it but it is nice when you see twisty roads vs straight roads on the screen. Plus when your done not paying any attention to where you are, just hit "go home"
Hope this helps. New to this forum and my first Harley (Road King) is only 3 days old but I have been riding my 2002 Vulcan Meanstreak with the 2720 on it for about 4 years and it has never let me down