I found Hyouka's Festival arc to be enjoyable due to the uncharacteristically natural way they handled the character interactions. I really liked how every character was off doing their own thing and acting like, you know, real people would during a school-wide activity, as opposed to wasting their time clinging to Oreki curious about some stupid ass shit that happened once, or wondering why the fuck they were mad about something the other day. I also liked the way the arc's shitty mystery was weaved into the background without interfering much with the overall narrative and as such, I quickly started losing interest once it was unavoidably brought into the forefront during the latter episodes.
I stand by my opinion that the festival arc, by virtue of the more energetic yet laidback feel that permeated through most of it, was a great respite from the show's usual formula of having the generally vacuous cast of characters illogically giving far too much importance to completely trivial "mysteries" and wasting their time on crap no one with actual shit to do would ever give two fucks about.