I've played three more games of Mouse Guard in the past few weeks. One has been with my wife and daughter, the other two with my regular gaming group.
The family game went as well as the first two, although it was somewhat constrained by bedtime. They had to defend a caravan of parties supplies from some mouse bandits - this led to a fight, which was a great success. They then had to deal with a bluejay trying to steal cake, which they had less luck with. Continues to be fun with a young kid - she had no problems at all with the concepts involved in the conflict mechanics for the fight, either.
For the regular group, we played out "Deliver the Mail" and then a mission to see what some mysterious sightings on a certain road were being caused by
The intricate details of these games aren't really such a big deal - the thing Mouse Guard really shines at is ease of play. You can sit down for 5-20 minutes and come up with some good ideas for a mission, but if you don't have time for that you can just pick a couple of things as you crack open the rulebook at the beginning of your session. The characters' beliefs and instincts give you really big clues as to what sort of things the players want to see, too.
As you play, failed rolls allow you to provide twists to the story, which is a perfect way to elaborate things as you go whenever you have a cool idea for what could happen next. The trait mechanics encourage players to choose to make rolls harder for themselves in order to gain checks to use later (I can see this becoming more common as people play more sessions and begin to really realise the power that checks have), which contributes too.
It ends up with the game seeming to reflect the choices that the group as a whole makes about where things should go, but without anyone having to try really hard to make it happen. I continue to recommend this game!