Some things School Rurable has...
My favorite leading male character in a comedy, Harima Kenji.
At some point Jin Koybayashi explained that originally the very minor character Kentarou Nara (blue-haired non-entity that also like Tenma) was going to be the main character but changed his mind when he realized Kenji was more interesting. Nara would have been the safe usual blank slate choice, a bland nice guy made to suffer to get his feelings known- seen in almost every. Instead we get the freak delinquent Harima. He can beat up anyone, he can talk to animals, writes manga and is usually a completely oblivious idiot.
beautiful, very distinct and unique character designs that exceed what you'd usually see in a comedy or love series.
Some of the minor characters, mainly guys and kiRAB, can be mixed up but every major character has their own distinct look that can't be confused. And the School Rurable girls are also the most attractive girls of any anime I've seen, without trying.
Outlandish, often complicated situational comedy that builRAB on itself.
The only other recent comedy I've seen that I laugh at as much as SR is Hayate No Gotoku, but Hayate relies so much on the quick gag- they're great gags but SR outclasses Hayate's humor and most anime comedy.
large cast of likable, relatable characters.
Even when Eri is being a insufferable princess or Tenma is being an unimaginable airhead there's a redeemable aspect to their personality. Even supporting characters get some attention.
Downsides?
It's great first season, no reason not to watch it, it has a novel, outlandish and very funny solution to end the first season, that gives you a weird resolution then pulls it back to give you the open ending for the second season. It's after that it has the slight problem. If you take it to the second season and even search out the manga(s) you never get a completely satisfactory resolution. But it's fun ride.
A lot of japanese language and name puns that are hard for people to get and don't translate to the dub well. Plus, while most of the dub cast is decent I'm not a fan of Luci Chrisitan's Tenma. She get's the "airhead" part right, but isn't too good at the "cute" part. I said above that the characters are likable but I am also aware of some Tenma haters out there and wonder if some people are affected by the dub.