Okay, spent a good while in practice with him. Some cool stuff of his:
-Roundhouse can be dash cancelled if you hold down 4. It also builds some good meter, even if cancelled.
-Teleport can be done in the air.
-Lightning to bubble works anywhere.
-Bubble leaves you standing, no matter what, so it gives Rain a great tool to prevent wakeup attacks.
-Boost gives you a damage boost, but you cannot block. Normal boost is slight and not worth using. EX Boost gives a HUGE damage boost...like...my combo of choice does 36% normally. With boost, it does 51%. So you can see the damage boost is insane. I think eventually, this will be a big tool for Rain.
From the looks of it, Rain is a very offensive character.