I rather liked the dynamic Saki2 and Nagisa were building up, in the initial chapters. The developmental threeway between them and Naoya was actually pretty interesting, and despite the obvious comedy of it, somehow vaguely believable in a strange surreal way; I really felt like it could and would all work out in the end. Then Rika was introduced and it all since taken a backseat to nonstop gags and the manga has lost that feeling. For that alone she will always be worst girl.
Still funny as hell though.