Thank you SDCVO for you update on this. I emailed Jon @ Horny Toad HD and he was willing to give a 10% discount and I was about to pull the trigger on it.
It is a real bummer that they do not include the TPMS option. I realize that you have to purchase the sensors separately, but having that ability would be really nice. This must be why the HD version is $100 less then the Garmin model.
I know that HD lists the device as a Zumo 590LM, but as far as LM goes, I see that HD does not list that as a feature in their descriptions for any of their currently listed Zumo's so I am suspect if it is there. In this day and age (and at this price) LM should be included with the GPS (along with that little device Twolanerider was asking about).

As a PS -- you will note that HD lists the product as a
Road Tech Zumo 590 Navigation System - Domestic and not the 590LM. When I search for a Garmin model it always comes up as a
590LM.