D&D last.

Healing and combat

Okay. Combat runs about as fast per combat as 3.x did.... however the structure is different. There are generally more monsters/bad guys per encounter, and rounds move faster, but there are more rounds. So something that would be a 20 minute fight in 3 rounds in 3.x is a 20 minute 5 or 6 round fight in 4th.
Powers were mentioned previously – dailys are once per day, per encounter are recharged between encounters, at will can be used anytime. Magic Missile is an at will for the mage, for example. Lots of these abilities move around allies, you or enemies. Combat is very tactical (but really no more so that full on mapped Hero combat). The different classes and roles focus on different things – Paladins and Fighters move enemies, and get enemies to stay on them, whereas Ranges and Rogues move around a lot. A lot the tactics in 4th is team playing, each player working to set up team attacks, or help teammates set up for a nasty attack. It fosters teamwork.

I really like that.

Healing is really different. One of the biggest complaints about the Cleric in 3rd ed is that he couldn't do fun stuff, but had to save up for healing. 4th has a compeltely different paradigm. Hit points have always been abstracted, but they extend this out to the rest of the healing system. Every character has “Healing Surges” that heal ¼ of his hit points. A character can take a second wind and heal that every encounter. And many classes (and some races) have abilities to use a healing surge due to the power (The Orc racial lets the orc get a healing surge anytime he hits a bloodied enemy). These surges represent energy, force of will, focus or whathave. A perfect example of a healing surge in movies is Inigo Montoya shaking off the thrown knife in the Princes Bride.
Another element is Bloodied, as mentioned above. You are bloodied when you hit half hit points. A number of abilities are triggered by this as well. That is the point where actually physical damage occurs.

Simulationist will generally hate this. I like it, or at least how it is handled here. I like that healing surges can be represented by any number of things in the – healing, an inspiring speech, or simple force of will.

One of the big changes the designers made is moving away from resource management. Apparently people didn't like that about older versions of D&D – so no more worrying how many spells you have for the day, or how many days you need to rest to get up to full strength. Encounter powers recharge between every fight, and one night's rest restores all daily abilities and heals all hit points, healing surges ect. So every morning you are full and ready to go.

I'm ambivalent about this, but it does make for a simpler game, and to be honest I do like that.

Encounters and adventure builders/monsters

Monster making is simple. Monsters have a role just like characters, and there is a chart in the DMG (or MM I don't recall) that gives you a basic grid of attack, defense, hits ect per role per monster level. This is for building monsters of your own – you just choose level, get numbers, add a power or two, and away you go. There are also some oddball – minions who have full attack and damage efforts, but one hit point of damage kills them. Then there are elites and solos – these are monsters that are tougher than others of their level. Every monster in the MM has a role, level and XP rating.

Each encounter is assumed to have 1 standard monster per character. An elite counts for 2 regular monsters and a solo counts for 5. Minions count for ¼. So you mix and match roles and power levels to get your encounter. Easy to build, easy to balance. It's actually a little more flexible than what I just described, but just as simple. :) (the actual mechanism using XP as a guide). There are also templates and such as well, that lay over creatures.

So it is amazingly simple to build monsters and encounters in the game, so the GMs job is much much easier. I love this as well – the reason I stopped playing 3.x is that the Wife GMed me, and it was solo play in our spare time, and once the game got to where I really enjoyed it (low teens) it took so much work to come up with encounters and adventures, we just stopped playing. Now that shouldn't be as much of a concern for us.

Final Overview
The game is limited, with very specific choices. Later books should expand that, but that will cost extra cash.
For my need, though, this game fits exactly. I've always like the trappings of D&D, so this is still a nostalgia trip for me.