How often is it updated? Apps like iHunter are also great resources if you pay for the public land layer.
In addition to knowing public/private land boundaries, it is also important to be aware of any municipal bylaws restricting discharge or firearms or no sunday gun hunting areas (except up north where this isn't an issue).
Updating would certainly be an issue as I bought the sd card 4 years ago and not updated since. Yes, one in our hunting group has a subscription to a hunting app that shows private land and his agrees with my Garmin.
Good point on the municipal bylaws. Years ago we were hunting in a lovely deer area well out of town but later found out that the town boundaries went out past where we were and my Garmin showed it as a WMU. We would have been in a bit of a pickle if seen that day…