There are some previews of the rules from DDXP. Some of the stuff I noticed, there are no more full-round actions (or the full attack). You get a standard action, move action, and minor action. Minor actions include stuff like drawing a weapon or opening a door. There are also free actions, these can now be taken at any time, not just on your turn (ie you can talk in-game even if its not your turn). There is also still immediate actions, but they seem incorporated a bit more (ie readied actions use immediate actions). Charge uses a standard action now, rather than a full-round (as those apparently don't exist anymore), but you only move up to your normal speed (instead of double). You can also charge through difficult terrain. The charge gives only a +1 to hit, but I think there is no longer an AC penalty.
A 5-foot step is no longer 'free', it takes your whole move action to make the 5-foot "shift" (as its called now). I think elves get a racial ability that lets them move 10 feet when making a shift instead of just 5 feet.
You only use your 'standard' attack for opportunity attacks (attacks of opportunity, guess they wanted to shorten the wording); the attacks you make on your turn instead use your at-will abilities, ie the rogue has one that is a lot like spring attack/shot on the run, and another one that lets him ignore armor.
Reach no longer automatically gives you more threatened squares, you also need a second ability called 'threatening reach' (or something like that).
Hit points are figured a bit different too. Rogues, for example, start with 12 + Constitution score in HP, and get 5 per lvl (no dice or Con mod). You get so many healing surges per day, rogue gets 6+ Con mod, I think fighter gets 9+ Con mod. A healing surge heals you 1/4 your normal max HP and takes a 5 minute rest to do. You can also, once per encounter as a standard action, use Second Wind, that lets you use a healing surge in combat. Clerics can make your healing surges cure more damage, and I think let you do them more than once inside combat.