Wow, yeah, lots of changes. Full screen map (thank god), Trading Mods and Keys in the Dojo, new UI (again) that I don't really like (again) but that will perhaps grow on me like the last iteration did. (What was wrong with the previous icon styles? I really dislike the look of these new ones, although the fully integrated options bar is nice, finally, everything all in one place.)
Some mod tweaks. Warframe skins. The Hunt for Alad V event. Several new bosses. A couple new weapons (shotguns it seems, and the Grineer Whip.) The new Berzerker Warframe Valkyre.
This is a damn big update. The core of it though, I dunno, I need more time with it. But it seems to have failed at its initial goal of reducing rainbow builds. There's even more reasons to pile more elements on your weapons. Sure, they've eliminated contradictory effects like burning guys being frozen, or frozen guys starting on fire. But they haven't really removed the reasons for putting 4 different elemental mods on your weapons. They've just reduced the # of effects you get out of it, and moved the proc effect to its own attribute separate from everything else. But that doesn't change the fact that highest damage = most effects, for the most part. In terms of DPS, I think stacking as many elements as you can after you've done the critical ones will still be tops. Half the elemental effects are fluff when guys will be dead in less than 2 seconds. Maybe it will matter more in high level play, where all this stuff will really be put to the the test. (Time to do some Void runs I think.)
Proc rate of elemental effects is now based on the "status chance" of a weapon, and it's something you can mod for. So hurray for not binding it to crit, although this means most enemies won't be paralyzed when you shoot them with a face full of fire unless you mod for it. It also adds yet another mod competing for space in your build. Which isn't necessarily a bad thing, but for most people it will probably mean they just rarely see their procs (see above why that won't matter for the majority of play.)
On top of that, they've changed the level scaling as well. Lvl 40 now = Lvl 100 from before. I was fighting level 15 guys earlier, but it was hard to really suss out how armor has changed. It's going to take a while to feel out how things are, because you still can't trust the math on the Arsenal page.
It's a lot to take in. Honestly, I think the most important thing out of this besides armor is the level scaling. Right before the last patch, people were posting videos of 5 hour survivals against 2000 level enemies. Clearly the game didn't have long-term balanced dialed in, and between the two changes I believe they're attempting to do that. But I think they're going to be doing a lot of tweaking on Thing 2.0. Because you can't upend game balance like that without breaking quite a few things. And all these changes are only a couple months in the making, on top of all the other Warframe updates.