As a whole the show is pretty much an average comedy series. The writing is clever and that should be recognized, but it's often built on references/genre styles and fall into the same traps other shows do. There are a couple of absolutely genius episodes that you must watch and the show shines when it pastiches movie genres to a tee. It's a recommendation from me but not a must watch. It's good but a lot of Dan Harmon fans praises it to the skies and ignores the shows weaknesses.

If you want a underrated show made by Dan Harmon you should watch "the Sarah Silverman program". It might be my favorite show of all times and it contains everything Dan Harmon does great without any of his weaknesses.