So what have I missed?

[BraveEarth]

I used to play with my local PFS group but it kind of went on hiatus for a while and I tried a few online games but eventually just took a big break from pathfinder in general. It's been about year and a half since then, and I've been looking to get back into Society play, and my basic question is there any huge things that I should be aware of? Other than the whole race change thing, which I'm kind of miffed at but oh well.

[GM Lamplighter]

There are 7 factions now, and almost all have changed names. There are about a hundred new classes available (ok, only 10, but still). Lots more, too - you should read the new Guide to Organized Play version 6.0.

[BigNorseWolf]

The aasimars and tieflings tagged out. (they needed to) Nagaji, wayangs, and kitsune tagged in.

The factions changed. Scarzini got a hostile take over from qadiria and are now the exchange.

Cheliax is now the dark archives, and devoted to dangerous forbidden knowledge being properly cared for. Not evil since AR 4314

Osirion is now the scarab sages, and under new leadership.

Andoran cut ties with andor and is now liberties edge. Still slave freeing do gooders though

Taldor is now the Sovereign court, trying to promote an international nobless obligee coalition of nobles that do something.

[Blackbot]

Blogpost II regarding factions
Blogpost III regarding factions
Blogpost IV regarding factions

Weird, IV does not appear if you're looking for society-posts, even though it's tagged as one.
Oh, and faction missions are gone/heavily changed, but you left at about the time this was announced I think, so nothing new for you there...?

[Bob Hopp]

I just came back after a similar break, and Core Campaign was a huge surprise to me. Basically, there is a separate PFS campaign wherein you can only take things for your character that are in the Core Rulebook. This goes for race, feats, class, equipment, etc. (unless a chronicle sheet gives you access). You can ignore that whole Core thing and just continue to play your existing characters, though.

However, it becomes important for you if you are signing up for a PFS scenario. If the GM is running the scenario for the Core Campaign, you won't be able to use your non-Core characters. For session reporting purposes, it's all or none: if it's going to be logged as Core, then only Core characters can play and get credit. If it's non-Core (I believe "Classic" is the term), then only non-Core characters can play and get credit. There can be no cross-pollination, so to speak.

Usually, GMs posting events for open signup are pretty clear, but if they just tack "(core)" on the end of the description & you don't know what that means, that could lead to frustration. As I said, this may not impact you at all, but I wanted to say something so you don't show up to play at a PFS table only to be told, "You can't play with us."

Good luck and welcome back!