I feel the restriction to hold your cities small to benefit from the high free upkeep for small towns in Feudalism is a real nuisance.
As is forced labor! You will probably not be able to use it, because your towns are actually around size 6 max.
Money-rushing will usually work better.
You can build cities in an ICS style or nearly as densely packed, that close city placement has starting benefits has been proven. Then you can rush with lots of military units.
I still dislike this playstyle, but the point is:
You can do this all in Monarchy and you will not have war weariness - it is not really serious, but you will have it. And in small cities weary people are harder to please than in large ones, one entertainer kills effectively 1/6 of your production e.g.
Republic has commerce benefits and many claim it to be more useful than Monarchy at all and stay the whole game in Republic - depending on game level of course.
You should also not forget that small towns need longer to produce military units. This will somewhat be compensated by sheer number of towns.
Finally, Ision said it sucks - and I say it, too.
I think there are too few situations where it is actually useful, and you are somewhat forced to play towards Feudalism right from the beginning. Ugh - I do not like it.