I had the HK nav on my 09 Ultra, and now have the 665 on my 11 FLHXSE2, and in my humble opinion, the 665 kicks-buttocks -- works flawlessly. I have the paid weather service as well, and this summer it saved my dry butt about 15 times -- i was able to outrun some storms, pulling over and the let fly by, reroute my trip for others, -- I'm trying to figure out what took Harley so long to provide the weather service on any nav device.
I have XM radio paid subscription, I use it on long trips, but have most of the songs played on XM either on the Ipod or in the 665 itself. Sometimes I use it to listen to talk radio and the weather channel, because I can only listen to Free Bird so many times. LOL
In sum, I would highly recommend it, and get the fairing mount -- less vibration so you can read it standing still.