My dear Harbinger has been doing the heavy listing on keeping track of D&D Next playtest reactions of late, and now the last public one is out. That said, Mearls and Co. are still making some extremely interesting Legends and Lore posts, and the most recent one has spurred me out of my complaisant atrophy to make some comments.
To begin with, I want to say that I am a huge fan of Four Core Classes, combine into neat-o concepts. This post addresses the former with the idea of Mage, Priest, Warrior, Trickster, but doesn't go into the latter at all, which is a bit disappointing. Trying to decide of the Monk is a Warrior or a Trickster (one or the other) is sort of silly IMHO; use the headers here as source types (which works for everyone except Trickster, really), and call a Monk a Trickster-Warrior (though I think of Monks as more Priesty-Warrior, like more-different flavored Paladins). Then you can have cool things like Magey-Priests, and Warrior-Mages, and so on.
The problem as I see it here is that they're kind of trying to re-create Defender, Striker, Leader, Controller without actually doing that, but they're using terms that don't exactly apply to the same things. It's kind of an un-developed idea in the post, but what will make or break it, I think, is how and whether they decide to handle overlap.
But then, I was a huge fan of Class/Background/Specialty, which sparked my imagination enough to create a Warlock with the priest background and a cool custom specialty of Harbinger's... which led to a neat story about an apostate priest who, not having been blessed with clerical powers, made a bargain with the Lords of the Fey, and belongs to an order who heals through bloodletting. I'm not saying that the current creation rules don't include things that will spark interesting story ideas (and a lot of the impetus for this idea came from the setting itself, to be fair), but in previous versions, I don't think it would have occurred to me to have a character who combined the divine and arcane, as there was really no good, supported way of expressing that idea mechanically. And the Priest Background kept it nicely limited. Personally (and while yes, I realise that there's a lot of mechanical variation and stuff they've done to legitimise it as a class), I'd have liked to see Paladins expressed solely as Fighters with the Priest background, or Clerics with the Warrior/Mercenary background (and related specialties), depending on their focus.
It should now not surprise you that I don't care for a whole lot of additional classes, on the whole. I think that the impetus to come up with a bunch of mechanics for said classes tends to result in those classes being Just Better than anything basic... as the Paladin is in the most current playtest packet. A traditional Paladin problem. Which then results in everyone's favorite game: Nerf the Pally. It's an unfortunate cycle.
Now, the chance of me running anything at all in the next... anytime soon is incredibly slim, but were I to do so, I would probably run out of some of those earlier packets, and keep the systems I like. Which is a definite advantage of the way the playtest has been run up to this point... we effectively have several partial, but playable games with a lot of different mechanics to pick, choose, and monkey around with. Which is awesome to me on a lot of levels, the most immediate of which is that I wouldn't ever run the current playtest as written-- I am sick to death of, "just start at 3rd level if you want to have fun" games, and that is very much where they've gone here.
I have some additional thoughts on the first part of the post-- spells, spell lists, and the like, but that is a topic for another post, if I can rouse myself enough to make one later.