In my opinion, HD really missed the mark when they put an HK system in the new bikes instead of a comparable Garmin system. The HK system has been plagued with problems since its introduction, although to be fair, they've released updates to resolve many of them. In general, I find the HK system more awkward to use and not as intuitive as Garmin's, but that may simply be because I've been using Garmin for 12 or 13 years and I'm used to it. HD also doesn't offer lifetime map updates like Garmin did. While Garmin released an updated map set every three months or so, NaviExtras (the folks who do the maps) doesn't seem to do it nearly as often and if their file naming system is any indication (the latest release is 2014Q2), they're two years behind, at least here in the States.
I guess my thoughts are to do your homework and play with the system as much as you can, learn its quirks, and give yourself a year or so to get used to it. It's not Garmin, but it's all we have to work with.