Alright, I just finished a game as Arabia on an archipelago map going full commerce (Beta 11), so here's what I've seen.
1) I think the change in Optics was a great one. Now that I can get a freshwater gold bonus even faster than a food one, it provides more incentives to build villages early. And then from there, I have more incentives to increase them through policies later.
2) Even with the nerf to the seaport its still a good building. Now its more about the production bonus to ships than the other benefits but its still solid. Meanwhile, the harbor is now a good building to build on almost any coastal city.
3) My policy strat this game was to start with a little bit of tradition (which overall was a mistake), then I got Honor -> Military Caste for the culture bonus. I then went all commerce.
I can say that Military Caste is right now the greatest culture bump you can get in the early game. I would build a city, buy a monument and place a warrior in the city, granting an immediate 4 culture in the city. Until you get temples there are so few ways to bump culture that its a big impact.
As for commerce, the bonuses were generally pretty nice. The golden age definitely fits the theme of commerce. The -25% unit cost was a nice transition point after that. I went with merchant navy next. It was funny that honestly for my archi game the naval bonuses were actually more useful than the hammer ones, mainly because I was always purchasing my important buildings. But that's good because the policy has different things for different games and that makes it a solid overall tech.
The lame duck was Guilds in this game. The +1 speed for embarked units was nice, but the -50% road cost was useless for me (I had 3 squares of roads in total). I choose it because I wanted to give the full tree a chance, but I was really tempting by other trees at that point. I see that in Beta 12 you changed it to +1 gold specialists. I think that's a great change, as that is more universally useful to all types of games.
Patent Law was a huge bonus for me...not for villages (I had some but not that many since I was mostly islands) but for the fish. I like your new change to bump the village bonus up more, but I disagree with the +4 to fishing boats. I think +2 is just fine, fish tiles are already insanely good late game (see my notes below).
I tried out Monopolization and got 13 happy off the bat, so it seems like an effective bonus.
Overall, my biggest problem was the fact that gold heavy games tend to lend themselves well to expansion, mainly because I gain get them up and running so quickly. But that means I get fewer policies, and every one of them is precious.
I went for a diplomatic (aka economic) win, and so commerce was very useful...but ultimately I wonder if the whole of the tree is good enough. Don't get me wrong, the bonuses are very nice. Its that if I am not getting money solely for money's sake, then is it the best route to go?
Commerce can help me buy science buildings for a science win...but then would rationalism be better?
Commerce can help me buy city stats for an dipl win...but couldn't patronage do the same thing?
Commerce can make specialists a bit better (+1 gold). But doesn't freedom make all specialists that much better?
Right now I find commerce is competing for attention with freedom for me. I find specialists are so powerful later in the game, especially on sea maps. I've got food at the wazoo, more specialist slots than I know what to do with, and a constant happiness problem.
The freedom tree makes my specialists even better, and the entry into that tree gives me a lot of happiness control by shifting citizens to specialists when happy is low. And of course 50% GG creation late game with a lot of specialists is great.
I think overall Commerce's greatest advantage right now is that it works with everything. I can go piety and commerce, commerce and rationalism. I can go commerce and autocracy for a late game war move, etc. I never go....damn, I really want to go X, but can't because I went commerce.
4) Naval Units are very powerful now. When you have a solid navy, no one is getting to your island....and you own coastal cities. The only real land defense is artillery until you have flight, which to me is how it should be. Now if we can just get the AI to understand that
Ships of the Line are a great use for iron in the midgame, but I like being able to build frigates if I don't have any. And ironclads are solid now. I might recommend lowering their stats a bit (they shouldn't have the same attack as destroyers imo). But the destroyers not needing iron and having twice the speed makes them very useful.
As a note, it might be worth lowering flight penalties against naval units. Naval units are much stronger than they used to be, I don't know if a big penalty is needed.
5) Properly done, fish tiles are the best tiles in the game. 6 F, 1 H, 5 G, 2 Sc. It really doesn't get better than that!
6) Does anyone see anything wrong with a civ that can build battleships but the strongest land unit he can field is a musketman?
