Tsubaki has a lot of uphill battles, especially against the top 3. She's not completely terrible, but she can hardly do any damage without charge, and building charge after a combo sacrifices any wakeup game she could have had. If you can somehow build up 3 charge stock though, she can be quite scary. Her 22D unblockable can mess with your opponent's head pretty badly, and she's got some very nice combos in the corner off of 22D and her throw with her Install. Her guard break game is kind of meh, and I believe only her 6C is a fatal counter, which comes out kind of slow and I really haven't seen any uses for it.
In all, she's decent. She doesn't have any hopeless matchups like Tager vs Nu in CT, just a few uphill ones. If you're only planning on playing online, I don't see any reason not to play her. I could see her perhaps holding you back if you were to play her in a large tournament just because of how common the top 3 are probably going to be.
I was a Litchi player and I'm picking her up though. I think she's a little underutilized perhaps. That being said, I'm still going to have Litchi as a second main.
Also, her Chibi sprites are awesome. I'm going to need to find a use for them.