Not great maybe, but way better than mediocre.
The combat is fun and most of the enemies are human or human like, which I prefer over spiders, snakes, or scorpions. The game is an action RPG in the vein of Ninja Gaiden or Dark Souls. I have put time in playing Conan for the PS3 as well, and Viking is a much better game than Conan.
The setting is very Viking. Your character is a lumbering hulk of a fellow who wields a sword in one hand and a battle ax in the other. You scale walls, sneak through occupied towns, ambush unsuspecting NPCs. You also engage groups or patrols in the open country, being watchful not to get surrounded or over powered, which will happen if you are not careful. I think some reviewers who dis this game haven't really played it to its full potential. It will become boring if you always choose to grunt your way through the combat, ignoring the other aspects of battle like stealth, sneaking up behind unsuspecting enemies for that critical slice and dice kill, using your range weapon for taking out sentries and loners. There are a number of attacks to learn for the sword and battle ax which deal out different kinds of damage and have different attack animations. For a special treat there are fatalities as a reward for pulling off a successful combo, complete with severed limbs , decapitations, and R rated blood!
The thing that is really different about Viking when comparing to other action RPGs are the times when you gather an entire army as an ally and storm a huge occupied city! At these times the game morphs into something like an RTS where you take command of the battle as a commanding general rather than a solo fighter. You call in air support in the form of fire breathing dragons that will wipe out whole placements of archers or infantry! Really pretty cool, and something I have never seen in a action RPG before.
I think the game deserves much more than a mediocre judgment, because even though it may not have deep RPG elements like complex weapons and armor upgrade paths, what it does have is done well and it makes for fun, exciting play.
If you are looking around for a hack and slash title and haven't played Viking you are missing a good one, well worth your time. Check it out.