Very entertaining if you're happy with a little sneaking, sword fights and plenty of gore.
However, most of the missions you must complete on your own, which means a lot of button mashing as you encounter your foes in hand-to-hand combat. These fights are spectacular in all their gore, yet the fighting itself is a bit uninspiring. You can purchase more advanced and spectacular fighting techniques at arenas, but the game doesn't invite the player to use this very extensively.
However, it doesn't serve the game justice to simply label it as a fighting game, as going into battle with full force often means a quick death. Several of the missions are better completed by sneaking into enemy encampments undetected, and reaching your goal with as little sword fight as possible. These missions are in fact a lot more intense than the pure fighting, as the level designers have carefully designed Skarin's path in-between hiding places and patrolling guards. It's really rewarding to observe your enemies from a distance, work out a strategy on how to proceed, and silently kill the enemy one by one as you proceed deeper into his territory.
This way, the game is a semi-linear mix between free-roaming around the map outside the missions, and more linearity within the missions themselves. It enables the player freedom of movement, yet presents carefully designed challenges. But there are really no reasons why you should free-roam the map, as there is very little to see, apart from some generic natural landscapes. If you play Viking for the exploration aspect, you'll be disappointed, but it works well to frame the missions and create an atmosphere around them.
The missions themselves could have been more fleshed out, as they're completed quite quickly once you've figured out how to approach them. The enemy seems to be quite ignorant of what goes on around him, and could have an increased awareness level if you made a mistake. I threw an explosive fire pot into an enemy crowd, and besides the guys who died, nobody seemed to be alerted and alarmed to investigation. But if the enemies do detect you, they'll be on your back at once, and as Skarin runs a bit slower than his enemies, trying to escape won't help you.
Viking doesn't revolutionize level design and gameplay, but it nicely combines stealth with fighting in a free-roaming context, with those large battle to spice it up. It's very entertaining if you're happy with a little sneaking, sword fights and plenty of gore.