I've got that ol' familiar feeling I get from these articles: disappointment, which is usually tempered by pleasant surprise when I see what they actually do in the playtest. For example, I hated the "fighter design goals" with a passion, but those goals somehow led to the CS fighter, which I am very excited about.
So that in mind, here are some responses:
"Casting mechanics at the system level, not at the class level" - I still think this idea gives up a lot of flavor and specificity in the name of "modularity." But let's see how they pull it off! I'm very glad to see warlocks got separated out of the "magic user" stew, so that they can preserve some unique mechanics. I wonder whether psions will be so lucky, as another class whose main feature pre-4e was that it provided an alternate spellcasting system.
Note that the "magic-user" metaclass they're talking about DOESN'T include the cleric. So again, do clerics get alternate spellcasting systems?
Now wizard traditions include apparently one extra cantrip and one "signature" spell that you get to cast twice. Really, what is the point of this signature spell? It sounds basically like one extra spell slot, but more limited. If they're going to introduce encounter spells, I'd think they should go whole hog with it,, especially if you get only ONE signature spell.
All the cleric changes sound like a step up from the second playtest. Yay, simplified mechanics! No more "channel divinity" that was only for healing except when it wasn't! I don't get at all why anyone insists on Turn Undead as a class feature, but sure, why not. Expanded domain powers/benefits sound great too.
One big note, though: we all get that they're officially giving up on siloing off healing, right? "Channel divinity" was an attempt to assuage the concerns of players who didn't like the pre-4e tendency for clerics to have to save all their spells for heals, but now it's gone. Does the 5e cleric even get the 3e cleric's spontaneous healing? Or does he literally have to make 30+% of his prepared spells Cure X Wounds?
Simple fighter option: sure! Options are nice! I'm not sure why this would take more than 5 minutes though. Get rid of CS, give fighters a static bonus to damage and hp (to make up for lost parry and deadly strike). There you go! Roughly on par with the normal fighter in terms of raw effectiveness, no muss and fuss.
For rogues, they're screwing with skill mastery a bit, which, sure. But how about those alternatives to sneak attack that keep getting floated? Is hide-attack-hide really the be-all end-all of rogue tactics?
Skill changes sound great, specialty changes sound... meh (I hope "stealth specialist" isn't a real title, or it's way more confusing than the previous system). Since this playtest goes up to 10, do we get "advanced" specialties for levels 6 and 9, or do you just pick a second specialty? (Either would work, I guess, but advanced specialties might be a lot more interesting.)