Denmark in Civ V is a Viking based civ, with two unique units, the berserker that comes with the amphibious promotion, and second is the Norwegian ski infantry that gets bonuses on snow terrain and hills. Danes' trait lets them move faster while embarked, and don't lose all their movement points when making landfall which can make for some nasty surprise attacks. The DLC also includes a scenario in which you fight for control of Northern Europe. In it, research, happiness and culture are all locked, letting you focus on massing an army to take England, and to win it you need to conquer English towns to build a number of shire courts before you can construct the "Domestate Book" in London (After conquering it of course).
Now then. I'm happy to see a scandinavian Civ make its entry on Civ V, naturally a Viking based one. The Civ itself is decently balanced, with strong invasion bonuses but nothing else, no unique buildings or traits that improve simming. I've played a number of games with the DLC enabled, and it makes for some fun play especially when you control Denmark in archipelago and continents maps. However, when you encounter Danes controlled by the AI, they are very puny. There doesn't seem to be any AI scripts for Denmark to play the Civ as its designed. Even on an archipelago map I just played on, when I encountered Denmark they were tiny, had barely expanded to nearby islands at all, made no incentive to expand onto enemy islands and just bent over to take it when I declared war. I had high hopes for Denmark to be the "Inca of Civ 4 at sea", but that is simply not the case. If you play Denmark yourself you can do some very agressive play on sea based maps, but unfortunately whenever you encounter AI Danes you can sit back and rest assured they will be effortless to conquer should you want to.
When buying the Denmark DLC you have the option of buying a bundle with a few extra map types, which I didn't opt into. I can swallow paying for extra civs with proper diplomacy menues and such, but I won't pay for maps when there's already an abundance of maps for free download from the Civ V mods section. I would recommend you do the same, don't pay for single maps when similar or better maps are very easily available already.
To sum up, I felt a bit scammed after paying for the Denmark DLC. It lacks AI scripts that lets the computer do anything meaningful with the Civ, making this a very low value purchase compared to modded civs that play better, sans the animated diplomacy screens.