Optimistic was touted as one of the few tracks on Kid A which could have been singles. It was played frequently across American alternative radio stations. It's one of the only guitar-based songs on the album, and is also, one of the only songs which doesn't differ too much from the Radiohead sound of old. Very catchy, and a fan favourite at live shows. Featuring Phil on what sounds like some kind of tribal village drums, the track has a certain historical feel to it. While managing to be one of those songs that can get stuck in your head for days at the same time.

Thom has been known to sing the chorus as "The best you can ain't good enough" at some live shows. The studio version chorus is "The best you can is good enough".