Started a new campaign with 1.5.6 and I must say I really like rebellions.
It does a good job slowing down greedy factions and add a nice flavor to the campaign as certain cities at the center of conflict areas will often be in revolt. In my campaign it's Lageta, that has been occupied by Empire, Sturgia and Battania and have seen like four rebellions. Gives a feeling of sacked, indomitable city.
New clans are useful too, to resplenish the lord pool as noble clan members dies on the battlefield. It is fun to watch them climb the ladder and receive multiple castles in their new faction. Adds a lot to the world dynamic in my opinion.
Then, since the feature is really cool, I would like to be an actor in rebellions !
Like with a roguery-based "Incite Revolt" action (decrease town loyalty by ambushing a garrison patrol) for example.
I hope we will see more world events like this (private feuds and civil wars please please ?).
Thanks for the hard work !