I don't see how a movie can be overhyped simply because it's reviewed well.
Perhaps overrated would be a more appropriate term, because this movie hasn't received nearly as much hype as something like Inception did.
I think it's a fine movie and worthy of positive reviews. After all, RT is just a representation of how many critics thought it was a positive or negative experience. However, few of the reviews have hyped it as a re-inventing of the genre or another Coen masterpiece. Most reviews state simply that it's a well-acted and well-produced western that is perfectly enjoyable, if much more conventional than what one might expect from the directors.