I wonder if furious cities will yield easier once a conquering army rolls in. If so, and there are SPs/units/wonders that can induce unhappiness in a foreign civ, it might be prudent to bombard your opponent with propaganda before rolling in your cannon. If you wanted to be extra Machiavellian, you could possibly gift Gandhi a few 1-pop cities, drive his metropolises into riots, and take them without the headache of dealing with a massive hostile population.
I'm curious, though, if the military penalty for angry cities only affect the garrison, or any units stationed near it.
Ancient advantages snowball into Modern advantages. If an Iroquois player Great Warpaths his way through a neighboring civ or two by 2000 BCE, they'll have a huge immediate advantage that, with effective leveraging, can win the game. It sounds like city assimilation is harder than in Civ4, so by taking care of that early, the Iroquois can get a huge lead on everyone else that'll last until 2050 CE. The advantages from abilities are only as good as the player makes them - a non-rushing Iroquois, is about as useful as a REX/smallpoxing Gandhi, is as useful as Rashid with closed borders, is as useful as Liz in a desert.
Just don't forget that more Mohawk-captured cities now means more Tanks later.