StoryFree download and free to play. There will, as usual in these types of things, be an online store where you can buy things. They list Dungeon packs, character slots, potions, character customization, and hired goons will all be available for purchase with Turbine Points. The interesting this I read on another site is that you can earn Turbine Points inside the game itself, so you can use the store without actually buying anything.
Monthly fee will still be there if you want it, with it giving more character slots and the like. You'll also receive 500 Turbine Points every month to spend in the store, so if you're doing that anyway it might be worth a sub. Kind of an interesting way to do both.
Anywho, I'll probably give it a spin.
EDIT
IGN previewEDIT2
DDO website has a nice
chart that shows the difference between VIPs (ie, subscribers) and the free players.