My thoughts on Core 19 after several more weeks of drafting it at FNM (and maybe around 20-30 drafts online):
I like it way more than I expected to. I felt that way early on, and that opinion has not changed. My enjoyment mainly for the reason that it is a slower format. I think you can really judge the speed of a format based on how much people value Divination, because Divination can be really bad in a fast format where you're just never going to be able to have the mana free to cast it, but it's great in a longer game where it just turns one card into two, and Divination feels like one of the better commons in the set. I also love the fact that counter-magic is highly playable in this set, I have always felt that treating counterspells as removals is one of the biggest traps new players fall into, and yet when I look at how games in M19 frequently play out, Essence Scatter starts to look a heck of a lot like a removal spell.
Core 19 also continues a trend that I feel started with Dominaria, which is managing to strike the perfect balance in pricing removal spells fairly. I started playing Magic in an era where Doom Blade was a common, and those days of having 2-mana kill spells at common are obviously never coming back. Then there was a period of several years where they swung hard in the opposite direction, where WotC struggled to print fair and efficient removal to answer the bombs that you inevitably encounter in any set; I sometimes get flashbacks to Theros where the black removal spells were Sip of Hemlock (a six-mana hard removal) and Pharika's Cure (BB to deal 2 damage to something) where all of the removal was too expensive or too narrow to feel good about playing it. Dominaria was the first set in a long time where I felt the removal was powerful enough but fairly costed for what it was, and Core 19 feels exactly the same way. Each color (bar green) basically gets two removal spells which you're happy to play at common (if you bend the definition of removal spell to include Essence Scatter), and all of the removal spells are cards that I'm happy to draft (with Take Vengeance being the one piece of removal whose usefulness is sort of dependent on what deck you're playing it in).
The main "issue" with Core 19 is the same "issue" that exists for every core set, which is that you can't really go deep on any of the archetypes, with Black/White lifegain being the main exception and even the BW lifegain deck doesn't go extremely deep. In sets in Ixalan (tribal synergies) or Dominaria (specific archetypes/themes for each color pairing), you needed to balance drafting enablers with payoffs, and you'd often run into situations where your evaluation of a specific card would vary depending on what part of the draft you encountered it; a card like River Heralds' Boon could be the best or worst card in your deck depending on how many merfolk you had. Core 19, conversely, feels like a set where pretty much every draft can be boiled down to "pick the good cards, don't pick the bad cards," and pretty much every deck ends up being just a collection of good cards. This is something that LSV pointed out in a recent episode of Limited Resources, where Sarkhan's Unsealing is a great example of something that looks like a "build-around" card, but the truth is that when you first-pick Sarkhan's Unsealing the optimal strategy is to just draft cards like Thornhide Wolves and Colossal Dreadmaw and Onakke Ogre, and these are just generically okay-to-decent cards that you could play in any random RG deck, so the difference between a mediocre RG deck and a good RG deck isn't about how synergistic your deck is, but how powerful your cards are.
All of that being said, none of this is inherently a criticism of the format. In fact, the fact that pretty much every draft boils down to "pick the good cards, don't pick the bad cards" means that drafting Core 19 feels like more a test of your fundamentals than your experience with that particular format. I think that can make it a gratifying experience for experience players (who feel rewarded for the time they've spent mastering those fundamentals) and also for newer players (who can use it as a way to learn those fundamentals without having to learn a ton of exceptions). It's much easier to master a format like this, and you can feel like you have a pretty good idea of what's going on in Core 19 even if you haven't played every archetype...which again, can be seen as both a good thing (easy to learn) and a bad thing (not a ton of replay value). And yet, despite the fact that none of the archetypes are particularly deep, and none of the bombs are particularly sweet, I keep on going back to it. There are some draft archetypes that keep drawing you in because of the allure of doing sweet things (like Ixalan block), and there are some draft archetypes that keep drawing you in because the gameplay is good and interactive (like Core 19). Dominaria was a really special set because it offered you the ability to do sweet things and go deep AND it also had very solid gameplay.
Since the last time I got to post in this thread, I've gotten to actually draft a lot of white decks (including RW), and white is indeed all it's cracked up to be. I think the biggest thing that White has going for it are two marque commons in Star-Crowned Stag and Pegasus Courser that kind of serve the function of both being pseudo 2-for-1's in the context of an aggressive deck: Stag adds a creature to your side of the board while invalidating one of your opponent's blockers, and Pegasus Courser can give flying to something that would otherwise get gummed up on the board, effectively giving you two fliers for the price of one. It also helps somewhat that there are two kinds of white decks: the aggressive ones that want Stag, and the defensive ones that want Take Vengeance, and so if you commit to playing the white aggressive deck you can pick up these cards more easily than something like, say, a Luminous Bonds (the kind of card that ANY white deck is going to want). Also, I've gotten to play Heroic Reinforcements, and that deck is sweet, I find myself hesitating to say that RW is the best deck in the format, and yet I struggle to name a deck that's better.
I've also ended up playing blue/black control a lot. Blue has an incredibly deep suite of counterspells, and black is also good at getting you to the late game; the black removal is obviously important, but Vampire Neonate has also been an importat piece of the puzzle that both serves as a blocker early on against aggressive decks while also providing a mana sink in the late game, and being able to hold up an Essence Scatter on your opponent's turn while having the option to use that mana to activate Neonate on the end step if you didn't use the counter is great. Both Blue and Black have the tools to get you to the late game, where you just start running away with things by getting value off your Divinations, chipping in with evasive creatures. I've also been extremely impressed with Gearsmith Guardian, which ends up just being a 5/5 in almost every game.
Green does feel like it gets the short end of the stick in a lot of ways, but I find myself picking up green in a lot of drafts where I find myself picking up a lot of removal early and then looking for a second color, the situation of, "Well, I have a bunch of black removal spells but not a lot of creatures, so I'll guess I'll move into green because I'm guaranteed to get some number of decently-sized creatures if I'm in green," and that doesn't sound amazing but the other colors are deep enough that it often ends up being enough. Green probably pairs best with red (which has the best early removal and also has 4-powered creatures if you get Colossal Majesty or Sarkhan's Unsealing as your payoff), with green black also being decent at just doing the "pile of good cards" thing.
So, I'm having a good time with Core 19, but that being said, I feel like I've already fully explored this format and pretty much every time I start a new draft it's "I want something to entertain me for the next hour" rather than "I'm ready to learn or experience something new." Guilds of Ravnica doesn't come out until October and that feels like an eternity away.