What I mostly hate is the inequity. Let me explain:

As United Provinces I took (and eliminated) France. The discontent level was so high that even with tax exemption and a full stack left as garrison I couldn't hold the province. Then I gave it to the Spanish in exchange for peace (secretly hoping for a revolt and a new France, maybe a new trade partner?). For the next 15 years, Spain/AI had no problem holding France with a minimal garrison (2 or 3 units).

I took it again. It is rioting again, even though Paris it's now garrisoned with a full stack of light dragoons and militia. I decided to keep France, no matter what, just to see how long it will take for it to calm down. It's like an experiment now. 8 turns later it's still tax exempted and still in the yellow/red. It costs me a lot of upkeep. Next time, I'll just sell those nice juicy fat national provinces I take.

If there's a secret on how the AI suppresses so efficiently newly conquered regions, I would love to find it out.