Principal strong and weak points:
Super strong oki, great space control, gets to put the opponent in constant 50/50’s even while she’s comboing them. Optimally designed for conditioning opponent, and well equipped to capitalize on that conditioning.
On the other side of the ledger, she’s ironically weak on defense, and can struggle mightily against either very patient or exceptionally erratic opponents. Unsafe on everything, and relies to a sometimes prohibitive degree on you being able to get a read on what someone wants to do.
Best/Worst Match Ups:
Worst MU’s: Riptor, Aria. High level Sadira can also be a problem.
Best MU’s: Tusk, Orchid, Kim Wu. Most players would add Wulf and Glacius to this as well, but I personally hate fighting both those characters. Sako’s interesting in that I don’t think she outright wins many MU’s, but I also don’t think she loses all that many fights either. I tend to think she goes even with almost the entirety of the cast, with your victory or defeat largely just a question of “how well did you use your tools to shut down the opponent’s game?” She almost always has options - the only question is if you’re using them wisely.
And yes @Marbledecker - I do currently disagree that Kan-Ra is one of her very best MU’s 
I do think she does very well against him though, particularly in S3. With a bit more play against him, I actually could see myself coming around to your point of view on this one.
Advanced setups/tips:
As Marble says, command grab resets are actually always good. Normal->ORZ->light linker->influence command grab reset is something like 25% damage. Off a one chance. That refills your wrath and gets you a meaty setup of your choice. So yeah, pretty good 
As a note, you should generally use medium influence for your command grab resets - the light one often hits too fast and will whiff off some things, and the heavy takes just a bit too long to come out. The medium one gives you a good blend of speed and range. Hisako can influence reset off almost any portion of her combo, so get creative with mixing them in there (heavy influence may be necessary if you’re doing it off of something like a medium AD, since those can be pretty long range). Once the opponent starts holding up, punish him with anti-jump out resets instead.
Air-ORZ is a great space control tool. Make sure it hits though - it’s got a lot of recovery on it if you whiff it completely. It’s also no longer positive, so we don’t get to push buttons after anymore. However, because it isn’t positive anymore, it now functions as a fantastic setup for tick grabs. If someone blocks an air-ORZ, buffer a light influence as you’re coming down. Light air-ORZ (the worst one on block) is -2, while a jab is 5 frames. Light influence hits in 3 frames, meaning that even in the worst case scenario, an opponent has to reversal the jab to get it out at the same time as your command grab. On the heavier air-ORZ’s (which are 0 on block), only DP or something with throw invincibility will outright beat the influence tick. Also, learn to tiger knee your air-ORZ’s - they have oodles of start-up, and the higher up you hit with them, the worse they are on block. I’m not a huge fan of TK’d air-ORZ instinct combos. They are not actually super hard to break if you’re familiar with the character, and more importantly, they take away a lot of instinct time that can be put to better use. Hisako can REALLY tack on damage once she’s in instinct, but she won’t do it (not really) by using her swaggy TK’d air-ORZ shenanigans.
Aside from the above air-ORZ scenario, never tick throw with influence. Influence has ■■■■■■ range and weird timing to try and tick with. When you tick with possession, always use the light one. All possessions do the same amount of damage, and the light one starts sucking them in the fastest.
For uses of her shadow air-ORZ, see this thread:
After flip-out, your go-to options are meaty influence and meaty cr.MK->rekka. Influence will beat blocks, and cr.MK will beat jump-outs.
Your personal opinion about her:
Fantastic character who gets slept on because she doesn’t have braindead offense and takes work. You will always be having to think about what your opponent is going to do to get good with her, and you have to have an understanding of how to condition someone to do what you want them to do at any given moment. Hisako doesn’t get to run “flow chart” offense very often - your oki and pressure is almost always a hard read of some form or another.
Current character balance, why do you play her, what’s the most fun aspect of her gameplay for you:
I think Hisako is the best she’s ever been. The biggest addition to her game is definitely the faster wrath refill - it lets you run an incredibly oppressively pressure game, and means that you’ve got a lot more license now to use her fantastic normals in neutral. Tier wise, I think she’s solidly middle of the pack. I disagreed vehemently with people putting her bottom tier last season, and I think there’s even less call to put her there this season. She’s hard to break, has great meterless and 1-meter damage, fantastic reset potential, and for almost the entire cast forces them to adjust their playstyle to account for her options. Even Shago doesn’t just get to run his game against Hisako, and that’s a very powerful strength in a FG with offense as crazy as KI’s.
I actually picked up Hisako primarily as a counterpick to Sadira, who I was maining at the time. Sadira mirrors are terribly, terribly boring, and I could not for the life of me block her cross-ups (later found out this was probably a function of display lag). I saw that counter didn’t care about cross-ups and basically said “yep, that’s my new pocket.” And then, lo and behold, I just found that I really, really enjoyed playing the ghost girl. She was just more fun that Sadie was, so I found myself playing her more and more until one day, I had to reluctantly admit that I was in fact a Hisako main with a pocket Sadira, and not the other way around.
The reason I find Sako fun is the fact that I have to always be thinking with her. Sadira was just a really flow-charty character, where once you get started it almost doesn’t matter who you’re playing against or what their options are - Sadira imposes her will on you, and you pretty much just have to take it. That’s fine as far as it goes, but it also gets pretty boring after a while. I like that Hisako has to constantly evaluate what her opponent’s options are, and strategically play her pressure game in such a way as to avoid or mitigate those options. I like the challenge of conditioning someone to do or not do something, and then punishing them for finally “learning” the lesson. It’s just incredibly satisfying, and a lot more rewarding than “haha - you can’t block my crazy, shenanigansy mixup where even I didn’t know what side I was on”. That’s what I love about Hisako, and why I’ve gone all in on specializing with her