Completely free, no subscription needed unless you want extras.
By extras, I mean stuff like XM Guardian that gives you weather, traffic alerts, fuel prices, etc. Without the extras the navigator works just like the old windshield mounted units. It displays a live map of where you currently are, and you can obviously set it to give you directions. The only thing you're not getting that the paid extra gives you is a heads up on construction or crash. If you come upon such things you can just tell it to diver you, and it will navigate around it.
I believe you are not entirely correct.
Without Guardian, I believe you lose the ability to tap on the microphone on the Nav screen and say something like "McDonald's" and have it do an online search for the nearest places of interest that match what you spoke.
Without the online search that comes with having Guardian, you are limited to searching for specific addresses, using the map data that is stored in the Uconnect.
The online searching actually works reasonably well. Trying to find POIs using only the built-in map data sucks. But, of course, you can always search for your destination in Maps on your phone and then manually enter the address into the truck's nav to have it navigate you there. It's just not NEARLY as convenient.
Personally, I extended my Guardian package - but just the remote package. I really like having the ability to use my phone to lock/unlock/remote start, and also to find a destination and then use Send'n'Go to send my destination to the nav in my truck.
The remote unlock has saved my bacon at least once, when I actually managed to lock my key fob in the bed of my truck. Using my phone to remote unlock worked, otherwise, I was going to have to call a locksmith.
IIRC, I was scuba diving and wanted to lock up my truck while I was in the water, but obviously couldn't take my fob with me. So, I took the valet key out of the fob and put the fob in the bed (with a tonneau cover), then locked up the whole truck. When I came back, I was able to unlock the driver's door with my valet key, but that set the alarm off and the truck wouldn't let me unlock my tailgate, so I couldn't get to my key fob. I was very happy to have Uconnect with the Guardian Remote subscription that day!
Side note: The only thing I miss about having a Ford truck is the keypad entry on the driver's door. That was SO handy for things like scuba diving or for riding my dirtbike in the woods and not wanting to carry my truck key on me. I could just imagine crashing my dirtbike and losing my key in the woods somewhere. Or just being able to park my truck with the key inside and then give the door code to a friend and let them get my truck to use. Or have it serviced and just tell the place to leave the truck outside with the key locked inside when they were done, so I could pick it up after hours. And on and on. It was so handy, and it's so annoying that nobody but Ford (Lincoln/Mercury) seems to have that. Probably something Ford patented and won't license to anyone else...