Attributes are no longer graded roughly from 0 to 5, but from 1 to 10 instead. Where a 1 is absolutely terrible and 10 is the peak of human ability. We still have Fitness, Intellect and Empathy but they've been joined by three secondary stats that are cheaper in Awareness, Willpower, and Resources
The aim with the three new Attributes is to add a bit of depth to characters, allowing more control over things that previously you couldn't have much of a say on. You now get to roll Awareness to spot a trap or catch a lie, instead of just praying it doesn't go through your Defense, for instance. Willpower similarly would be used when you want to resist torture or walk through fire, without leaving it all up to the offensive roll. Resources, meanwhile, streamlines equipment rules a bit and handles things like wealth and contacts without leaving them entirely to the realm of abstraction.
It boils down to "More interaction = More fun." with a bit of extra PC customization on the side. The only thing that might be raising some questions is why the change in scale. That has to do with Skills. Speaking of which...
Skills are no longer a bonus from 1 to 5, now they're Advantages to their respective Tests. They can give from one to two Advantages to all appropriate Tests, and being untrained simply means not having any Advantages to your Test. Test no longer feels like a word by now. That said, they are more expensive now, which is why Specializations do the same thing but are cheaper, instead of being kinda good and kinda bad.
This cleans up the math a lot. No, it wasn't particularly difficult before the change, but tracking 6 items is easier than a full dozen. For the most part the benefit is that it allows Attributes to be the workhorse for basically everything. I can use Attributes do all sorts of things from a design standpoint, and a PC can Test an Attribute raw without needing to add a Skill bonus on top just to avoid sucking.
Also of note are Miracle Skills, what used to be the old Aberrant Skills, for psychic power shenanigans and assorted juju. They are exactly the same as regular Skills, except that their use always takes off some of your Plot Armor whether you fail or pass. Danger! Excitement! More on Plot Armor later!
Most of the old Traits came back, after a cost reshuffle and power adjusting where necessary, and they are a lot more like Upgrades now. Most have an unique effect applicable a limited number of times per session. But there is a good number of new Traits too, mostly for those dealing with new Attributes.
It does not stop there though! There's also specific categories for Traits known as Deathblows and Assets. Deathblows are modifiers to an Offensive Test that let you make an attack more accurate, hit multiple enemies at once, or stunning them for a little while. Assets encourage the use of Resources more aggressively, throwing around the weight of bribes or political backing to things you want done now, as long as you are willing to repay the favor later. Both Deathblows and Assets are cheap, ranging from 1 to 5 in PP, since their use is much more limited than that of Skills or other Traits.
Equipment is also listed under Traits, and the only significant changes would be that it is now more streamlined thanks to Resources, and that characters without significant Resources cannot access chemical weapons or suits of power armor.
Defense and Plot Armor
These have been revamped entirely. You have only one Defense and only one type of Plot Armor, and both work off your stats, leaving your Genre alone. Awareness contributes to Defense, while Willpower is much like Mecha Threshold. There's also only three Layers to Plot Armor now, for Damage that lasts Scenes, Episodes, and Arcs. There's also no more Consequences attached to said Damage, so it is simpler to work with.
As amazing as I personally found it to yell at people until they had hilarious meltdowns Phoenix Wright-style, the game is probably better off tracking only physical damage and mental integrity, so that's what Plot Armor shields you from. At least by default, no one is saying there cannot be a Miracle that makes you piss off people so bad they throw their toupee at you screaming bloody vengeance, but that's later.
Overall this boils down to simpler, cleaner interactions with things - or the ability to interact at all. Deathbows make ground-level combat a bit more fun for anyone who actually wants an emphasis on that, and Assets outright solve problems for stalled groups, at a price.
There's also been a few changes to Mecha rules - nothing really big, but still red-text worthy - which I'll talk more about when the Update proper strikes, because that's what everyone cares more about anyway. For the most part we're looking at a few increases to starting stats (mostly on the defensive side of things), revamped, Combinations that should represent the thing they're trying to be in a more clean and faithful fashion, and some Features being added to the Mecha Construction section (replacing Terrain Adaptability where necessary), plus the usual small balance adjustments here and there and oh look I wrote a whole paragraph about it anyway let's cut that short now.