Just four cards, but they really improve the game. No longer can you easily guess which colors your opponents need. It almost seems like the designer had a better idea for scoring that he was able to add with these cards.
I would say that if you've played Runewars a couple times and like it enough to keep playing, you should get this expansion. The new cards are great, and I also really like using the more powerful cities. I am not sure the commanders are worth the trouble though. Nothing here changes the game too much, but the added variety is great to have.