your opinion on katarina?

She's a pubstomp champion. People who have minimal CC or fail to CC well, Kat will stomp out the competition. If she's against people with lots of CC or against a lane bully in lane, she'll get stomped and be useless late. She's a feast or famine champion that requires timing (When to go in. Can't go in until the CC you're afraid of is used.), patience, and 20 MPen in your masteries so you can ignore as much of the huge amount of MR that will be built to keep you killing them.

I'd say there are other mid laners that are better. Quite a few, actually. Most can do her job at a range or quicker or have a better time laning like Diana, LeBlanc, Veigar, Zed... Lots, really. She's got a one-up on any laner that doesn't have CC and/or mobility.

She's also a high-skill champ. I don't mean her kit is hard. Her kit is mechanically -very- easy. She's got two targeted abilities and two Play Based Area of Effect (PBAoE) abilities. Having an easy to use kit doesn't mean she's easy as a whole. Avoiding CC is quite hard when your only defense is a 15% damage reduc for 1.5s.

Beyond that, your laning phase usually requires you to have your jungle gank. If your jungle doesn't gank, your lane gets pushed in, you miss out on farm, your opponent gets to roam, and you're sittin' there spamming MIA pings hoping your allies are paying attention to pings.