I did some math to see how good Sorcerous Burst is on average, now that it's a d8. Because these are averages, I'm only looking at additional bonus dice added from the base dice, because the chances of rolling a second round of bonus dice is so minuscule (even at lvl17) that they don't affect the average damage significantly.

From levels 1-4, you roll 1d8 as a base, which means you have a 12.5% chance to roll one 8 and get a bonus damage dice. Each 1d8 has an average damage of 4.5, so your average damage is 4.5 + (12.5%)(4.5) = 5.06. That's still less than a Firebolt's average of 5.5, but you do get to change your damage type every turn AND you're more likely to do 10 or more damage than a Firebolt (10% chance of 10 damage, vs (12.5%)(87.5%) = 10.9% chance of rolling an 8 and then at least a 2 to deal 10+ damage). At the same time, Sorcerous Burst is much more likely to do negligible damage than a Firebolt. A 5e goblin has 7 HP, for example. If you hit one with Firebolt, you have a 4/10 = 40% chance to deal at least enough damage to kill it with one shot from full health. If you hit one with Sorcerous Burst, however, you have a 2/8 = 25% chance to deal enough damage to kill them.

From levels 5-9, you roll 2d8, which gives you a 21.88% chance of rolling exactly one 8, and a 1.56% chance of rolling two 8s, for a total average damage of 10.13 (vs Firebolt's 11). At lvl11, the average damage goes to 15.19 (vs 16.5), and at lvl17 it goes to 20.25 (vs 22). So it's the same pattern at every level: Firebolt does more on average, but Sorcerous Burst has better chance to deal high damage, has a much higher potential damage cap, and its damage can be changed if damage type matters...while it also has a greater chance of doing a small amount of damage. It is, in short, a swingy and unpredictable spell, which is very thematic.

I think Sorcerous Burst is the right pick for a sorcerer looking for a damage-dealing cantrip. It's not strictly better than Firebolt, and is more likely both to overkill its targets and to not deal enough damage when you need it to, but it's also more likely to surprise you and deal way more damage than you thought it would. It's also more likely to be useful as a damage-dealer in more situations, since you can change its damage type.

World Tree barbarian looks neat.

The brawler fighter has one glaring oversight: it has no way to apply magic damage while using its class features. They promise to include magic items in the DMG that will allow them to do so (probably gauntlets, rings, etc...) but as it is, the class is essentially useless beyond level 5. Unless you find a magic beer bottle or something.

Warlocks are still gimped. While having Agonizing Blast and Eldritch Spear apply to any cantrip is a great change (edit: though there is a huge oversight still which makes Eldritch Blast still the optimal and obvious choice, namely that Agonizing Blast lets you add the charisma modifier to each damage roll, and at the cantrip improvement levels EB gains new damage rolls instead of extra damage dice like, say, fire bolt), they still lost their short rest spell recovery. If they could use the Magical Cunning PB/LR instead of 1/LR, that might be fair but as it is, a level 20 warlock has effectively 6 spell slots. And they can't even claim that it was to get rid of the short rest because the wizard's Arcane Recovery (which at level 20 can restore effectively the same amount and level of spell slots as the warlock's Magical Cunning, btw.) is still tied to it. (Also, while there are many Eldritch Invocations that give warlocks a free utility spell, the wizard's level 18 feature effectively gives them two of these for free, and they get to select any spell.)

Such a shame, it looks like the lvl 19 ASI increase doesn't play well with the Barbarian Capstone.

Two steps forward, one step back. Classes have unique capstone features, but the old bad ones are just kind of the same?

I like the idea of Studied Attacks...but at the same time, I don't like how it makes it impossible to roll your 3-5 attacks at once, because the order of your attacks (and whether you hit or miss with a previous attack) matters.

Oh good, they finally addressed how the "X Savant" (the wizard school discount feature) actually incentivizes you to not take spells of the appropriate school on level-up, and hope you find them as scrolls to copy them later. It actually does what it should do now: give you more spells of a particular school.

Also, Memorize Spell means that the wizard is now not only the best utility caster for rituals, they're the best utility caster, period. Every weird, niche spell that could be useful but only if you happened to prepare it on the right day is now available to you with just a minute of prep time. That's simply fantastic, I love it.