Okay, as promised, my reasoning.
Ordinarily I would agree with Konqrr that Kitana's hard matches are worse than what I feel they are, mostly due to characters with strong keep outs just outside of her sweep range (Jax, Liu, Scorp come to mind). Square Wave is ok but still does little to combat the strong outside sweep range position the above characters have to keep her offense at bay. However, there exists a technique to help alleviate that problem.
I guess I'll call it Hop Fan.
Most Kitana players release air fans anywhere from shortly after the apex of her jump to when she's about to land. Works ok, great for combos, but not difficult to react to and has limited setups. Hop Fan changes that quite a bit. It's pretty obvious what it is; simply a short u/f, u, or u/b jump off the ground into an air fan, well before she even reaches the apex of her jump. The significance of this is two-fold, so I suppose I'll nerd it up and analyze what it does for those that haven't faced it (and I'm not trying to insult intelligence or anything here, so bare with me):
1. Gives her a Mileena-like quality like the dreaded Hop Sai. The difference is that while Kitana's fan releases quickly, it's a bit slower and has a thick, nasty hitbox. Unlike Mileena however, Kitana uses this to move in those crucial half or full steps when she lands, while Mileena tends to move or leap back. I suppose it works in the vein of UMK3 Kitana air fan into run; except in a far more subtle manner.
2. Allows constant 33% damage scenarios against most of the characters in the game. Short hops in any direction where she wins the air-to-air battle should almost always lead to the air fan being tacked on, giving her Jax j/k, backbreaker damage but with slightly better range. Gives opponents that have great air moves or even air throws pause since her air normals have very high priority. Against tall characters (pretty much everyone but Liu, Shang, and the bitches) a hop kick when they're grounded will allow the air fan to connect for 33%.
What makes it work is that it's CRUCIAL for getting in on opponents. Hop Fan can be predicted and countered, but it cannot be reacted to. By the time you see it when it's unexpected, it forces that small hesitation...enough for her to walk in that crucial half or full step into her range, countering the constant keep-out space. When people start getting used to it, now she can mix it with Square Wave; full, blatant jumps with an attack or without (for better landing recovery to put on the pokes); or by blatantly walking into range which makes it SIGNIFICANTLY easier for her to get in. As MGP and MBK raised the potential of Jax and Liu from great to godly, Kitana NEEDS this ability to be competitive in not only those matches but against any top tier or otherwise difficult match and I feel it must be VERY consistent. Without it, I agree that those matches are about as bad as Konqrr says.
With that in mind, now to the match-ups...