Plants vs Zombies: Garden Warfare is due out next week, and more details are still trickling out. A hands-on narrated by Microsoft's Larry Hryb (aka Major Nelson) sheds some light on the various class abilities, and the in-game economy.
In the video, we get a look at each of the classes and their special abilities, with some explanation of when those tactics might come in handy. You can summon extra plants or zombies to help the war effort, but as Hryb notes, those reinforcements have their limits. You unlock them using sticker books, which are bought in the store using coins earned from matches.
The stickers come in packs that are randomized and hidden, similar to purchasing packs in Mass Effect 3. Producer Brian Lindley recently told GameSpot that it will have no microtransactions at launch, but that economy certainly seems to lend itself to adding purchasable packs eventually.