GPSCity have also already included it in their comparisons page.
I set it up to the compare the Montana 650t to the 62ST, Zumo 550 and Zumo 660 here
as three of the more popular Garmin options for motorcycles.
You can't take all that the comparison lists, as it says no to a headphone jack, but then they show a headphone jack on the Montana 600 in the videos
I'd imagine that some of the red crosses against features are due to them not being listed by Garmin yet.
It does look like an intriguing option for a GPSr though.