Last night I actually read the whole thing, only semi-watching MNF, which sort of fits within the theme of a Norse rpg: the giants of the NFL traveled to a cloudy, misty land, defeated by a surly group of individuals who won the battle due to interference from the gods. Yes, that game was ridiculous. Where are the real refs? Yggdrasill is not ridiculous, and it's a reasonably good game, but it's kind of boring. Nothing about this game really stands apart mechanically. In fact, I kept thinking that Dragon Warriors would be a better system to use as it has a similar feel.
Lots of flavor text help maintain the atmosphere yet provide nothing compelling when it's all over. I can't really say what it is about this game that I dislike, as I don't dislike it at all; it just isn't that interesting. Playing Vikings (the game specifically states its not about vikings due to the temporal component of that term) can go one of two ways: cinematic and badass or realistic and morose. Yggsdrasill goes with the second, attempting to maintain a very historical view of Norsemen. And then it throws in magic and stuff. So, really it's not "historical", but instead Norse myth (good), tries to put those myths in a historical context (also good), and maintains the tone inherent in those myths (great). This does not make a fun game.
I'm not really that interested in being playing mellow games about inevitable doom. Perhaps this game is not directed at me, then, because Norse myth is about fate and dying and gloomy crap. Just like it can be argued that Middle Earth is a terrible roleplaying world (I'm not entirely convinced but I definitely understand the sentiment), this is not a game you pick up and play every so often. It takes a commitment to engage in a game such as this due to the subject matter. This is not a casual rpg whatsoever.
Should you buy it? If you were to ask me to recommend an rpg that accurately captures Norse myth, this would be it. In fact, the only other game with a true Scandinavian bent I can think of is MEGA*, and it pretty much sucks. Yes, I own that, too. But do you really want to play in that environment? I'm sure there are groups who wish to explore such areas in their "serious gameplay", so yeah, get this. If you are looking for something a bit more lighthearted, I suggest the Spongebob Viking game I mentioned above.
*Don't talk to me about Rune...that hardly counts. And of course I own that.