Should I buy MOW:AS?

[XFriendlyFireX]

I've seen people say it's the best in the series,and after playing the demo,I really liked it.

But one thing,is the online still alive?Do a good amount of people still play online? I don't want to buy it just for SP and be stuck with that.

Also,including DLC,how many nations are there?

Any information would be greatly appreciated.