Well, it'll be very interesting to hear what they do next as a full album, as half the band left....

(From wiki) - On July 6, 2009 it was announced, via the band's official website, that both Ryan Ross and Jon Walker had left the band due to musical differences. The two are currently in a new band, The Young Veins, and are finished with their first album Take a Vacation, and are trying to release it. Brendon Urie and Spencer Smith are to continue performing as Panic! at the Disco. This changed the plans for the third album, which they will now write and record without the help of either of Ross or Walker.

...from what I recall, guitarist Ross was the one who pushed for the sound of their last album, which was very much a departure from the first. I'm sure since there were mixed reactions to it - I don't think it sold as well, even though it's a far better album - it's what led to the split. The new single sounds more like their earlier work, but is still good.