The story was lackluster, and events tended to happen because the plot demanded it.
The characters weren't all that interesting, and the secondary club members were basically there to fill space.
The ending felt like a copout, although I'm not really surprised. While I was hoping for a more bittersweet ending in which Nanasawa comes to terms with not getting together with Seto, it's fairly obvious that the story was going this direction since the older Nanasawa confessed.
That said, it had its moments, so I'd call it a guilty pleasure.