We've got two clerics, a wizard, a rogue and a fighter of various races. Each character has 4 primary "aspects" their Race, their Class, their Background and their Theme.
Races: The races are interesting, although completely traditional. There's no sign of dragonborn or tieflings here. Probably a good thing, I was pretty ambivalent when they were first introduced as a player race but when they started getting shoehorned into every single setting it got fairly ridiculous. The racial abilities are all familiar to those who played D&D before: elves have keen senses, dwarves are hardy, etc. They make good use of the "advantage" mechanics here.
The first thing one notices upon examining races is that racial abilities are significantly more powerful here. Dwarves for instance, are straight up immune to poison (but how do they get drunk!?) for instance and elves are likewise immune to charm and always have advantage when making perception rolls. there's no indication of what benefits a human receives, but their ability scores are notably much higher than the other races.
They seem to be reintroducing the "subraces" from 2e. We've got a hill and mountain dwarf, and the elf is a "high elf" and halfling is a "lightfoot halfling". There's no sign of what exactly the differences are however.
Class: The classes presented so far are the 4 classics: fighter, cleric, wizard and rogue. I think we're all familiar with them. There's no sign of what other classes will eventually be available but the playing guide notes charisma can serve as a magical ability so presumably we'll at least be seeing some sort of sorcerer/bard thing. The class abilities are all very generic and familiar and we can definitely see the return of vancian magic and almost no sign of 4e's powers (although there's a few holdovers here and there like the cleric's Channel Divinity ability)
It's worth noting that Rogues seem to have had the biggest facelift. They've got a load of abilities, some of them very impressive, like the fact that for any skill they're trained in the minimum result is going to be 10...that's the minimum die result. Meaning that if that halfling rogue wants to make a Stealth check he's rolling a minimum of 16. That's impressive to say the least. They seem to be really trying to push the rogue as the skill monkey again (rather than the "slayer" it was in 4e), although it's worth noting that sneak attacking is much easier than 2e and 3e (all you need is some form of Advantage. At second level the rogue gets the ability to give himself advantage on rolls 2 times a day. The fighter deserves mention as well for the Fighter Surge ability which grants the ability to take extra actions a few times a day at 2nd level. Hopefully this indicates that they'll manage to keep fighters and rogues interesting in comparison to spellcasters.
The rogue and cleric seem to have "subclasses", the cleric is based on the god they worship and the rogue has a "scheme" (in this case thief) which seems to indicate what "kind" of rogue they'll be.
Background: Now here's something new. Your Background is an aspect which is independent of class/race and provides you with your skill training. In the playtest we've got Soldier, Commoner, Sage, Priest and Knight. Theoretically these can be swapped to any class so if you had a wizard who serves the god of magic then you might have a Wizard + Priest, or if a hedge witch you might go Wizard + Commoner. Each background comes with skill training in a selection of skills and a special ability. These abilities range from pretty weak to pretty nice. The Commoner is probably the worst, you get training in 3 skills (where most others get 4) and the "Trade" ability is not at all impressive. This could indicate a serious balance problem (especially since backgrounds are available equally to everyone...why take anything but the best?) but it's far too earlier to say. There could be plenty of things that help to balance stuff out.
That aside I'm very impressed with some of the ideas in backgrounds, most of them seem designed to serve as interesting plot and roleplaying hooks rather than just + X bonuses. They're geared towards social effects and the Sage ability Researcher is an incredible piece of work for just two sentences. Researcher means that if you fail a knowledge roll to recall or learn a fact then you automatically know where you can find the answer (such as the great library of XX or the sage of YY) it's a great idea and something I plan to try and work into other games
However, I'm also concerned with the fact that many of these abilities are so socially based that it "locks you in" to a single ability. For instance, you've got a commoner...what happens if later on you accomplish a major mission for the king and are knighted...do you gain the Knight background and lose all your commoner abilities? What about a Knight or a Priest who (in the course of the game) is cast out from their order or is otherwise prevented from taking advantage of their abilities...can they change backgrounds? what happens to their skills? These are questions that I hope will be answered in time.
Theme: Theme, like background, is a general trait that can be added to any class. They seem to fill the "character role" niche. For instance you've got the Guardian theme which is the shield-toting defender type who can protect others, the slayer is good at killing folks, etc. Again these range from relatively weak (the Slayer theme, which means that if you miss you inflict a small amount of damage anyway) to really powerful (the Healer theme, which maximizes all healing rolls you make, lets you make cheap healing potions and maximizes recovery for your allies). However, it's far too early to say for sure since the themes seem designed to increase in power as you level up.
Overall: I like a lot of what I'm seeing. It actually resembles a fusion of 2e and 3e so far, with a dab or two of 4e here and there. Time will tell if this is good or not. Looking through the classes I have only one big concern and that is in regard to multiclassing and flexibility. The theme and background should let you customize your individual fighter or wizard easily...but I'm not sure how they'll be handling multiclassing or the ability to start gaining new skills or abilities later in play. This is one of the things I really liked about 3e. If, after playing for several levels, you decide you'd like your fighter to invest a little bit in a side ability like stealth or even spellcasting, you can just pop a level into another class or even just pick up a different feat or set of skills. We'll see.
So, there's not a huge amount to go on but my first impression is cautiously optimistic. I'm not seeing a lot of the flags that turned me off of 4e and I'm seeing a lot of really impressive new ideas and little tricks to make things interesting. I can definitely say I plan on buying it when it comes out, but I can't say for sure if I'll invest in it as a primary system. That said, I think we'll need to see a lot more unique stuff before 5e becomes really successful, there's a lot of markets right now. So far here's what I think you'll think:
If you don't like D&D: This product is not for you. This is still D&D to the core and if it didn't appeal to you already then you won't find anything new to love here.
If you're a die-hard 4e fan: I don't think you'll like 5e very much. It's got a few trappings stolen from 4e, but overall it rejects the previous edition pretty heavily. I doubt you'll want to switch.
If you're a 3e hold-out: Then you'll probably want to give this edition a try. It's resemblance to 3e is very strong and it looks like there's a definite effort to try and fix some of 3e's issues.
If you're an old-schooler: You might want to give this a look. It definitely looks like wizards noticed the Old School revival going on and there's a lot of things that indicate that they're trying to appeal to the old guard, 2e and before grognards. I certainly can't say for sure until the game is actually released but it seems like they're trying to recapture the feel of the old-school with some more modern mechanics. The playtest character sheets even mention dropping Background and Theme for an "old-school" feel. Whether this is really worthy or just pandering only time will tell.
If you're one of the many D&D fans taken by Pathfinder: This is me right now, D&D isn't necessarily my go-to game but when I play I pull out my gigantic Pathfinder book. Is 5e going to displace pathfinder as my game-of-choice...I don't know and I don't think I'll be able to say until I actually get a look at the full book...but I think there's a solid chance it might do the job.