We played a one-shot using Reign. My idea was to have everyone roll random characters, see what we got and then either point-build or roll a company for them. After that, I'd grab some of the companies I made up, pick some as antagonists and let it all roll, driven by the players' plans for their company.
This overall structure worked well. We had a variety of down on their luck but previously important characters, and they rolled a small coastal area as their company. One-roll character generation was a success in this context, creating some interesting characters that gave everyone some unusual elements to build on - perhaps the coolest was the bastard who was stranded and raised by animals as a child. We decided that they had been shuffled out of the way by the king for various reasons, and put in charge of this impoverished border county.
After some initial discussions, they decided to go after the rebels in the hills, mainly as a way to build up the county - their first raid was intended to loot all the rebels' goods. After some misadventures in the early stages, this became personal and over the course of the evening they conquered the rebels utterly. We also had some other side-plots, with a religious sect, some mercenaries and one PC's (doomed) attempt to take the company's influence rating above zero (so that he could be the spymaster that he claimed to be).
We had to abbreviate a lot to fit in the company action, leaving most of the PC missions down to a single scene or two. Given longer term play, these would be much more of a focus (and thus much more fun). On the other hand, we gave the company rules a decent workout and had a lot of fun.
Positives: The company stuff worked well, and gives you some easy goals in play. The world has some cool features, that added some good colour (although I was fairly cautious about infodumps, I did a couple on major points - geography and ghosts as I recall).
Negatives: The magic system and esoteric disciplines are pretty over the top for a one shot - there's a lot to take in. Almost certainly this is a non-issue for medium or long term play.