Beowulf is a computer animated 3D movie, which itself is presented in 3D. That makes the movie, by my maths, nine dimensional, which is at least four more dimensions than the human mind is equipped to cope with.
I spent the first quarter-hour or so of the movie unable to process the 3D effect; then something clicked, and I rather enjoyed the rest. It gets full credit for actually staying true to the format of a 1500-year old Danish epic; it's unapologetic about its narrative asides, over-the-top embellishment, and carnal focus. By the same token, as a modern audience you'll likely feel a little odd about its utter unwillingness to see the majority of its characters develop, grow, overcome obstacles, of find narrative closure.
Plus there's a lot of nudity. A LOT of nudity. You have to remember that back in those days clothes were nests for ticks and other parasites and it was actually more convenient to take them off prior to ruling your kingdom, going to war, fighting a troll, or humiliating enemy prisoners. Historical fact, honest.
All round, it's worth seeing. Director Robert Zemeckis is generally a purveyor of cinema which falls short of art but easily delivers fun, and Beowulf is no exception. Don't expect the world, and you'll be pleasantly surprised by what you get instead.