Wizards posted them yesterday. Many were hoping that this would preview a lot of 4E combat changes, but that doesn’t appear to be the case. Nonetheless, there were a few changes that stood out to me from the previous version of the DDM rules:

• No more morale! Previously, a big part of the game was keeping your commanders near your warband. That seems to be gone, along with morale saves for half HPs (though the 4E Bloodied condition makes an appearance) and routing rules.
• The new starter set comes with a (slightly goofy looking) Green Dragon. Definitely a good thing to get started.
• Factions are changed. Instead of alignment based ones, there are: Borderlands, Civilization, Wilderness, and Underdark. Alignment is still in the game: Good and Evil creatures don’t work together, but Unaligned work with everybody.
• Attacks of Opportunity are still around, in much of the same way as the old game. Though they are called “Opportunity Attacks” now.
• Crit rules are the same as the old DDM game (and not like the 4e crits): Natural 20 auto-hits and does double damage.
• Diagonal movement now costs only one square, ever. This is much easier.
• Charging is a bit different- it’s an attack action that grants a +1 to hit and allows a move and attack, provided you don’t move afterwards. (So basically, you use it to double move, though there may be some reason to spend the move action.)
• Combat Advantage is listed, which probably will appear in 4E. Basically, Combat Advantage rolls in a number of other conditions from before- you gain it from flanking, being invisible, etc., and it lets you sneak attack.
• More icon driven: Melee, Ranged, and Magic Blastiness all have their own icons that work differently, and clearly delineate them.
• Commanders are gone, but we get Champions instead, who have special powers that look like they’ll have to be managed carefully for what you want to do… moreso than just getting a Commander into an area.

Overall, I like the changes, but I still don’t think it’s simple enough to get anyone to play with me. It’s still somewhat complex, and has enough differences from core D&D to require me to teach a full game.

Edit: Wizards has done their own recap of the changes, along with some design commentary. Check it out.