I tried my spearman/swordsman rush again this time. I've been going with a 5 city opener and failing miserably, so this time I tried a 4 city start to go into the push. I got a really good start for this one, several cities with strong production, and iron in immediate vicinity. After getting 4 tributes with my spears, I teched to swords, getting my first swordsman out of turn 67.
Ultimately was in a war with Byznatium till turn 122 (with one 10 turn peace). I bagged the statue of zeus and used the early heroic epic with Japan's GG bonus to get my first set of GA, GW, and GM. I finally got to push the capital and take, vassalizing Byzantium. So here are my thoughts:
1) The CS boost for the sword is noticeable in the field on defense. When your huddled in forest, the sword can take a good amount of punishment. Also, skirmishers definitely do less than they used to. Byzantium was using them a lot, and it was good that my swords could take some hits from them, even if they couldn't return the favor.
2) That said, the problem with swords is, cities in decent defensive positions (aka forests) with walls don't care if you have spears and swords, ultimately if you don't have cats its really hard to do enough damage to the city before you have to pull back and heal. I don't feel the new swords did anything different in that respect. A lot of my time was just dancing around the cities, because once I committed, while I didn't lose any swords, I just couldn't hold there long enough with swords alone. I still have to rely on my Catapults for damage.
3) This leads me to suggest a change I've thrown out before, change Shock I out for Drill I with swords. This will give Swords a strong anti-city niche, and combined with their normal promotion can give them enough city killing power to maaaaybe substitute for cats...maybe (probably not, but maybe). And then horses can focus on shock like they already do, and you have 2 nice clear lines.
4) I am falling in love with the new overrun, its juicy! That said, I am bouncing back and forth between it and march for my samurai so I think its balance is about right.
5) Happiness wise, the 4 city base helped a lot. I still slipped several times into crippling unhappiness, but some of that was the length of my wars and war weariness. That said, you can only realistically hold about 1 maybe 2 cities and that point in the game, otherwise your happiness craters until you get courthouses. I literally gave one of the cities I took from Byzantium back to him because of a revolt (btw, I though revolts were supposed to become CS now?)...but I took the capital immediately afterward and vassaled, so I wasn't too mad.
6) Ultimately in trying out this swords focused play...I can see some use in the hands of a melee focused player like Japan. But I still don't feel I'm getting anything more than I would have gotten going my usual military tradition / mathematics opening...and I still backfilled those techs anyway to get the cats and barracks I needed.
7) Skirmishers still beat Spears, even if the skirmishers have a little rough terrain to move around in. The fact is, the skirmisher can move in and attack the spear...with the change though they stay there after the attack. Ultimately the damaged spear does a little less damage, and the skirmisher can capitalize. So he ultimately still wins, but the difference is he takes a good amount of damage for the effort.
I think its in a much more reasonable place, and I do agree this new rough terrain penalty is superior to the last one. Skirmishers still pack a punch, but I no longer dread them (and focus on them) in my play, they are now a good unit to have, but not a dominant one to push with.