A promising entry to the series, Warrior of the North delivers great new content but is hampered by bugs and design.
On the one hand, you get a new faction (the Vikings), more spells and units and a new pet mechanic (the Valkyries). But on the other, you'll find a host of bugs come with the new material - and I should know, since I created and managed the official bugs post on the forums since the day the game came out (seriously, look for my username in the game's credits). While the same great minds must have designed the new content (all of it is interesting and fun, in my opinion) it must have been handed off to a different QA or development studio for implementation. The developers have been fixing bugs in patches that have come out roughly once a month, but at the time of this writing there are still a significant number of them outstanding.
The other thing limiting my praise is a design decision that, on the surface, seems splendid. KB: WoTN allows you more freedom to choose where you want to go and which enemies to fight very early... much earlier than in other entries in the series. On the plus side, this allows you to grow powerful at your own pace, picking and choosing every encounter. On the minus side, you will quickly reach a point where you can overcome every challenge... but then you're left with dozens and dozens of meaningless, trivial fights on every map. The careful pacing of earlier series ensured more longevity than this, and frankly I struggled to keep going once I realized the endgame had gone from a victory lap to a victory marathon (this was on Normal difficulty, I should add).
That said, I am giving it a 7.5 because it's still King's Bounty and the new units, spells and concepts add more flavor and variety to the game. The art is great, the maps well made and the dialog (when translated correctly) as quirky as ever. I still had a lot of fun crafting the perfect army and polishing my hero into a mighty force. I just wish that sweet spot had lasted longer.
If you're a fan of the series, I think you'll enjoy it... but don't expect it to hold you till the end.