Boomkins definitely have some tools now.
Not sure how they will be, in relation to other options; time will tell.
I'd think the team will do well in Battlegrounds, but not be the best in Arena.

Entangling Roots will be an instant-cast, via Glyph.
Cyclone remains an option too.
You can silence your opposition, in a small AoE.
You have the option for stealth/surprise attacks.
Mushrooms will be some defense (counterattack) against melee or melee cleave.