...I think of 3rd Edition kind of like a first generation console video game in that sometimes it isn't programmed very efficiently. Ever played a first-gen game and seen the "slowdown" effect, where the system can't keep up with the graphics or the number of bad guys on screen? That's how I feel about 3E these days. I like what it's trying to accomplish, but it just doesn't happen very efficiently and things slow to a crawl. 4E on the other hand is like a late-gen game; the programmers have learned better ways to do things on the console, and as such you have even better games that don't experience as many slowdowns.
Basic design things that caught my attention:
- You are not your loot. There's no longer this equipment = power value. In 3.x, the game required that you have a specific value in magic items or you were under or over powered. That's gone.
- Encounter design. There's no longer the boring encounter ratio regarding using your resources. This should play a lot like urban campaigning where you're always challenged with every encounter, since you can instantly go get healing at the local temple.
- Vancian Magic Gored. Yes! Say goodbye to memorize and forget. Both Wizards and Sorcerers will still be included.
- Social Encounters. They have mechanics for social interaction rather than a flat Diplomacy check. I'll reserve judgement on this one, but I really hope it's good.
- No Feat Chains. But we still have prestige classes. There's a conscious effort to remove the "character planning" requirement in which you need to know where your character will be at 20th level when you first roll them up.
- Clunky Combat. It sounds like they're doing away with such favorites as Attacks of Opportunity, along with the infamous Grapple rules and other mechanics that are too complex or too clunky.
- Action Characters. Every character will have actions they can perform at will, per encounter or per day. If you've ever played a sidelined character because they used their one special ability and can't do it again for a good long time (the paladin smiting evil was an example given), you know what I mean.
- D20 and OGL. It's still open source.
If all this pans out, 4.0 should address a lot of the issues that have driven people away from Dungeons & Dragons.