I told myself I wasn't going to get sucked back in, I really did. But hey - Gen 2 Pokemon have finally arrived in Pokemon GO, and I'm weak-willed. So here I am.
There are a bunch of new Pokemon in this generation from the Johto region; you might recognize the starters Cyndaquil, Totodile, and Chikorita among the ranks. There's absolutely no way I'm going to catalog all of them here (there are like 80) but there are two that the GO community has locked onto with laser sights: Espeon and Umbreon.
You might remember that prior to this update, Eevee could evolve into one of three Pokemon: Flareon, Vaporeon, and Jolteon. Niantic, in their infinite glory, decided to continue the naming trick, which means that if you give your Eevee a specific name then it will evolve accordingly (though it only works once).
I'm putting this in its own paragraph because it's, in my opinion, the most important part of the update. If you want an Espeon, nickname your chosen Eevee "Sakura." If you want an Umbreon, nickname your chosen Eevee "Tamao." (These are nods to two trainers in the actual anime, one of whom owned an Umbreon and the other of whom owned an Espeon.)
If you're interested in the other features of this update, here they are:
The update is live now, so go check it out - and if you log on before February 28, upgrades to Pokemon storage are 50% off. You're going to need more space, after all.