I'm not sure when they will be done adding content, but I've enjoyed the few plays I've managed.
I didn't play Civ V, but Civ IV was very good and I'd say Vi is better.
Military is a little more challenging, though the AI still never really manages navies very well which is highly exploitable.

But, still a pretty fun game. I'd say the main thing missing is a true map editor like existed in 4.