Gurren Lagann is, at its heart, a mecha anime and, as anyone who knows my love of Transformers and Battletech will understand, that is a plus in my book. The art is great and the battle scenes are just awesome. On top of that, there are some pretty great characters in the show; I am especially fond of Kamina. Also, Gurren Lagann has already run its full 27 episode course, which means that I can watch it and enjoy a degree of completion, which is a thing that I really enjoy being able to do.
As far as anime series go, Gurren Lagann is the first one that I've seen and really enjoyed since Trigun. I wouldn't say that Gurren Lagann is not Samurai Champloo caliber but it's certainly worth hunting down and giving a shot.