So let's get to it.
We've got two "new" mechanics and of them I think only one really has the potential to be a pain in the ass for a long time.
So I'll start with the balanced one: Improvise. We all know this is just Convoke but for artifacts, right? Right.
But there's nothing wrong with that. While it's not my favorite mechanic, Convoke is useful and has at least one card that sees play fairly often across a variety of formats. And I believe Improvise is better, because you can use any artifact-the mechanic doesn't care if it's a creature or mana rock or just a Clue token. Any artifact that doesn't use the tap symbol to activate now has 'T: add 1 colorless to your mana pool' with this mechanic and that's a pretty strong place to be. Because creatures have value if untapped-but artifacts? You could go either way!
The fact that it's in Blue (which it should be but c'mon WotC, Artifacts are already Blue's color) helps; the splashes in Black and Red mean that they're at least trying to spread the power around.
The other mechanic, Revolt, has the potential to be one of the most annoying Standard mechanics in a long time. I don't know that it will be but I remember Thragtusk and people were really, really sick of that card by the time it left Standard.
Now we have a whole set that wants to engage in "leaves play" shenanigans. It's not quite on the same power level as Thragtusk, of course, but it does mean that Blue and White forms of removal have dropped down a notch. In addition, there are more cards overall that engage in the "flicker" mechanic since Thragtusk's printing.
So I think this has the potential to be really interesting and/or really bothersome and the broader the format, the greater the impact. Of those, Solemn Recruit, Fatal Push, Hidden Herbalists, Hidden Stockpile, and Renegade Rallier have some interest but the first three are clear winners.
Also: How do you have a mechanic called Revolt and not include it in Red? This is a massive flavor fail for WotC. Sorry folks; if they're going to demand that mechanics and flavor mesh then I don't see how you get around excluding the most chaotic color from a revolution.
Moving on to some more specific cards:
In White, let's talk about Sram and his Expertise. Sram is great, there's just no getting around it: he wants to play nice with a few of White's themes, giving him a broad base to work from. He won't make Bestow awesome but he at least brings an interesting dimension to what White likes to do. While the initial effect of his Expertise isn't great, a free spell is a free spell and I am hard pressed to think of a time in Magic's history where a free spell couldn't be broken or didn't tilt things unfun. At four mana, it's likely to see play, too. I expect good things here.
Blue has two cards I want to talk about too: Baral and Mechanized Production. The former because its second ability sucks. Decks that play this play it for the cost reduction of spells. Mechanized Production though, is a fascinating win condition that I hope people get to have fun with. I can definitely see this in a grindy deck that uses hexproof artifacts to pull out the win and I dig it.
Black gets interesting for a few reasons. Herald of Anguish feels like a card that was thrown together. Improvise and the sac ability have some synergy at least and flying is pretty standard for a demon but why is there a discard ability in the middle? There isn't anything about that ability that plays into the rest of the card, so it feels like an ability tacked on so they can make it a mythic. Renegade's Getaway's clause of "target permanent" feels weird too, because it can protect anything, including lands, enchantments and planeswalkers which I'm not sure Black should be able to protect. Yahenni's Expertise should become an excellent sweeper, too: unlike Baral's Expertise, Yahenni's is useful and cheap.
Red is notable for the shitty, shitty artifact destruction that is there and jeeze that's dumb. C'mon. Also, why isn't Chandra's Revolution an enchantment like her mom's? This feels...weird. Plus, they have zero thematic cohesion. Make up your mind's, WotC! Either this is something we're supposed to notice or it isn't!
As I get to Green, only Monstrous Onslaught really seems interesting because it's a potential low-level Wrath for Green. But it's incredibly situational and needs a massive creature: It seems like the kind of card that's good after you've lost the game. There's also a cat monkey (Scrounging Bandar), so hey, there's that.
Actually, I take it back: Unbridled Growth is probably really good. Color fixing until you don't need it, then it replaces itself. That's actually really good.
Gold cards are, aside from the planeswalkers, kinda 'eh' until Winding Constrictor comes up. This is the kind of card that makes me think it will have interactions with the next set, because of the "whenever you get a counter, you get an extra counter" clause.
Finally, the artifacts just..don't inspire me. They aren't awful but they don't do anything that unusual either, in my opinion. Spire of Industry has some pretty cool uses as a land but I'm a little discouraged to see it at rare, since it's fairly conditional as a five color mana generator and punishing when it turns on.