Not surprising; Chun's got options for days, as long as she's on her feet. Just from casual use, it seems like her touchiest aspect is her wake-up game. EX SBK is punishable in various ways and she's easily blown up by safejumps.
Probably the downside of having the best backdash in the game [her or Rose]. Even option-select sweeps can miss her, which can be really annoying.
Yup. Speaking as an SF4 Chun main, it used to be that EX Spinning Bird was her go-to wakeup option.
But, these days everyone knows it. More often than not, they will actively try to bait you into doing it so they can punish. Do nothing (block) or focus cancel to backdash is what she usually does these days.
Her worst matchups include divekick and mixup heavy characters: Viper, Rufus, Akuma, and I think Yun no thanks to AE.
...best danbooru discussion I have been part of, ever.