My opinions on the units:
Chukos: good skirmisher unit (is the 5 attack all 3 arrows or is the dmg done actually 15? anyone?)
Pikemen: only good vs cav. Aztec spearman is much better.
Changdao: lacks far behind dopps or sams.
Arquebusiers: there are better skirmishers in the game.
Keshik: useless.
Steppe rider: good in colonial perhaps. Later on, I just don't think it can keep up with cuirs or upgraded hussars for example.
I would like to hear your opinions on the Chinese.
