CGI has its strengths and weaknesses. For some reason the eyes don't look right, and a couple of times it Harrihausened itself.
I'd say it was like a good Disney film - say Beauty and the Beast or Peter Pan - made more explicitly violent. And it has the backbone of - gosh, I don't know the word - I don't mean authenticity. But you know like a decent Disney film or fairy story makes you feel it had some purpose to it. It's not demeaning.
I think if you take it on that basis, with that expectation, you'll get a good two hours of entertainment.
And - you'll have to trust me, my voice is doing a brilliant Ray Winstone impression here, even if my typing can't quite match it - 'I'm Beowulf: I'm 'ere to kiww your monsta.'
ETA - may I recommend rozk's review of Beowulf at Strange Horizons.