To enjoy, you must be in the correct frame of mind

Rating: 8/10 (13 July 2012)

MINOR SPOILERS! Nothing too serious.
As stated above, you need to understand what the creators of this film were attempting. This is not a realistic retelling of the tale (Beowulf and Grendel), nor is it just a cheesy action flick (Christopher Lambert's Beowulf). It's not a straight-up film adaptation, or a character study (most of you are out the door at this point). This is an analysis on the creation and destruction of heroes and villains. They just used Beowulf, Grendel and the others involved most likely because it is the most significant.
For Beowulf, the character, three different aspects show how the creation (or destruction) of a hero can happen. The first, and most obvious, is the storyteller's creative liberties. As is expected, the original tale is elaborated on to make the hero's dealings greater than they actually were. The second is satanic (or evil, if you wish) dealings. Beowulf becomes wealthy and world-famous due to mystical means, often times used to create villains, but shows that it's not always the case. The third is religion (true or false, it matters not for the sake of the film). As its influence spreads, the older beliefs and icons must be either destroyed or reshaped (meaning the said religion could have either destroyed Beowulf's tale, which gave strength to the older ones, or they could reshape it to fit their own religion, which gives strength to their own following).
As one aware of Beowulf's tale should know, it's not just about the hero but the villains he faces, and they are taken into account as well. For Grendel, his turn to malicious means is due solely to pain. The pain of his existence, and the pain of knowing that others are out there that are not suffering as he is. The mother's nature is due to both revenge (which is of course expected) and justification (Beowulf broke the deal, ergo she can do as she wishes). And the dragon is not so much evil by nature, but by nurture (he only does what he is told, we can presume).
The above was really for the nay-sayers of the film. Everything else in the film is quite strong. The visual effects are gorgeous (save for dead-pan eyes), the acting is amazing, and the action is awesome. I saw this in 2D, which for the most part is fine, although there were a couple of shots here and there that were obviously meant to show off the 3D.
Overall, it is a VERY good film, but you HAVE to look at it for what it is, and not what it's based on. Otherwise, haters are just gonna hate.