I think it's worth it. I enjoyed the game a lot, and if you're a fan of GOW3 then you should like Dante's Inferno as well. The PS3 version also includes the DLC content for free that you would otherwise have to pay for. Gives you a prequel level with new enemies and bosses, a new costume and new relics.
So yea I'd say it's definitely worth the $27, especially if you're a fan of similar games.