Most notable are the game's user interface changes. The PvZ2 map has been redesigned to make it easier for players to read, while in that same vein PopCap has introduced a number of smaller tweaks that should make it easier for players to "know how much you've done, where you're going, and what loot you'll get along the way."
In the realm of the truly new, PopCap has introduced a fast-forward button that speeds both planting times and the advancing zombie hordes. Likewise, the studio has also introduced new "Piñata Party" stages which offer big prizes, though this positive is counterbalanced by an ominous warning that this update has somehow made it more likely for players to encounter the gigantic, ultra-tough Gargantuar zombies during normal gameplay.
If you haven't already been introduced to the life-draining, productivity-smashing joys of Plants Vs Zombies, now is a great time to do so. You can find free-to-play iterations of Plants Vs Zombies 2 on both iTunes and Google Play, and while both are supported by microtransactions, it's entirely possible to play the game from start to finish without ever spending a dime.