Man, no more automatic countering. But that means as a player you don't get auto-countered either

So... as a level 5 spellcaster, counterspell a 9th level spell... if they roll bad...????

Uhh... not sure about this change

The slot isn't used, so at best it just delays the caster one round.

Not really sure I like this change tbh

So every single spellcaster (including paladins who want to smite apparently) will take resilient constitution now…got it.

This is so ******* ass

'which you take when you see a creature within 60 feet of yourself casting a spell with Verbal, Somatic, or Material components.

The wording here is weird. So only if a spell has V, or S, or M can you counterspell. Not if a spell has V and S, or V and M and so on...
This has to be a mistake, right?

I interpreted this to mean that a spell cannot be countered if it does not include any V, S or M components. 

No, it just means as long as the spell has at least one of the three, you can use Counterspell. It's like if you go to a restaurant and ask if they have diet Coke or root beer. If they have both, the answer is still yes.

I think this is a great change. It's essentially a spellcasting delay. This makes a lot of sense. Harry Potter feels like a low-level wizard compared to Voldemort, but even he was able to deflect/delay his spells. It's not a perfect comparison, but it conveys my point.

I agree that it would feel weird for a 5th-level wizard to be able to completely eliminate the spell slot of an 18th-level wizard, like if the 18th-level wizard is casting Power Word Kill (9th level spell) and the 5th-level wizard uses a 3rd level Counterspell and succeeds, wasting the whole 9th level spell slot. But now that Counterspell simply cancels the casting but does not cause the target to lose the spell slot? That's way more balanced.

Plus, as was pointed out, this is no longer an auto-cancel for PCs. Now it allows for a PC to make a saving throw. That's much more player agency than before.

Is it great that it's a Constitution saving throw? To me it is, but maybe others don't agree. But that's easy to house rule if you feel it necessary.

One thing I do really love about this new version is the specificity of what triggers the reaction. It makes it even more clear that things like Subtle Spell are super useful for being able to cast your spell without potential interruption. This makes the Metamagic Adept feat great for wizards and warlocks.

This applies to the old Counterspell and new one here but can you counter a spell that is cast using an Item?
The Item doesn't need any components like V, S or M so it wouldn't trigger the prerequisites for counterspell right?

even if you cast the spell through the item, you still have to cast it with its V, S, M requirements.

So if you are classing it from a Ring of Spell Storing you need to do V & S to cast it into the ring and then again to cast it out of the ring?

What is the save score? I know it's CON but is it 10 or 10 plus something? It's very unclear what the number to hit is.

against the counterspeller's spell save DC i assume

Quote from ReduxApex >>

What is the save score? I know it's CON but is it 10 or 10 plus something? It's very unclear what the number to hit is.

 The same as every other spell's save DC... It is the Spell Save DC of the person casting Counterspell.

Man, it'll sure feel great to see the big bad gearing up to kill one of my party members with power word kill, use my reaction and burn a spell slot to try and stop him, only to hear
"Legendary resistance. Your counterspell fails and your ally dies. Them's the breaks."

Like, real talk, being able to save against Counter Spell is ACTUALLY bad. Yes, it means you as a player can get out of being counter spelled. What it's going to more practically mean is that taking Counterspell in to battles with high level spellcasting threats is a fool's errand and there will be no way to counteract them.

Quote from Zelma >>

even if you cast the spell through the item, you still have to cast it with its V, S, M requirements.

 I don't believe that is correct, unless the item specifies it. 

"Some magic items allow the user to cast a spell from the item. The spell is cast at the lowest possible spell and caster level, doesn't expend any of the user's spell slots, and requires no components, unless the item's description says otherwise."  

Wand of Fireballs: "This wand has 7 charges. While holding it, you can use an action to expend 1 or more of its charges to cast the fireball spell (save DC 15) from it."  No mention of using a command word, or even pointing it at your target so RAW it cannot be counterspelled.

Ah yes, can't wait to go up against any creature post cr10 with advantage on its saving throws vs spell effects, and a +10 to +18 to con saves.

So in my understanding the spell caster doesn't loose his spell slot if successfully counterspelled and had used a/his spell slot but the counterspeller looses a 3rd level slot ... only to win one single round. What the hell should be the reason for me to use counterspell at all? There are only very special conditions where it makes sense ... the spell is weakend and far to expensive for the small benefit remaining. Other meanings?