Ok we changed our cities around to ARN on the in bound and CPH on the out bound.

From what I can tell it seems the best bet is to take the Arlanda Express train. There will be 2 people or will a cab be cheaper? faster? We have a day room at The Scandic Continental which is across from the Train station.

Are there round-trip same day tkts that would be cheaper?

Any info will be appreciated including what not to miss. We get in @ 7am and have a connecting flight out @ 8pm