Seamus went to the play, more to support his housemates and avoid his Potions homework than out of any great love for Shakespeare. All in all, he had a pretty good time (and Neville, you will be getting teased about those tights later, just so you know), even if it confirmed his suspicions that that kind of theatre wasn't really his thing.
He did enjoy the Slytherins getting their arses handed to them by Nev's mum though. A lot. He might have been heard laughing his head off when it happened.