Aside from graphical errors like the black terrain that can only be fixed by restarting the game multiple times..
I encountered a bug that after selecting a new merchant and telling it to start trading.. a little floating text "start trading" would appear next to my pointer, and then after that no matter how many new units I selected I couldn't perform any special abilities with any of the other units, and that text would not go away.
Sometimes during single player matches the prestige meter stays on top of the purchase unit screen and makes it difficult to purchase new units.
I do love this game. Please keep working on it!