Honestly, this is one of my favorite anime of all time, and it features one of my favorite characters, Usui.
With that being said, I will attempt to give an extremely helpful and encouraging review (and by "encouraging", I mean, "you must watch this ASAP").
One of the best parts of this anime is the humor. It's witty and really well-thought-out, if at times being slightly inappropriate. Every single episode had me cluthing my stomach, and often times, laughing until I cried.
The storyline of this show is, in my opinion, irrelevant. There are reoccuring themes and characters, but it is mostly episodic and focuses on the character development. The lack of a really in-depth storyline did not bother me, however. This is a shoujo, slice-of-life, romantic, in-school comedy anime, and I just don't feel like a storyline is necessary. The show is still infinitely better than other anime that aim to have a really wonderful storyline.
Mentioned previously is the character development. It's realistic without being boring. The lead female, Misaki, is stubborn, extreme, and a bit prejudice towards males (but who can blame her considering her daddy issues and the behavior of some of the males in her school). But as the show progresses, you start to see her grow as a person because of the catalyst that is Usui. He's loyal and goes out of his way to humor Misaki (because she can be a little competitve).
Lastly, I feel obligated to mention that part of the humor that is a part of this show is all in the drawing of the anime. You'll see what I mean with the three former-gang-members-turned-ultimate-Misaki-fans.
If I haven't convinced you to watch this show, then I have failed. This is one of the few anime I re-watch often. I can be extremely picky with anime, especially in the realm of shoujo, but this show has met all my standards and has gone above and beyond what I had expected before actually seeing an episode.
WATCH THE SHOW. YOU WON'T REGRET IT.