Hi, there.
I'm playing in a Dawnforge campaign right now. We're using the
Dawnforge CS as our main book, of course, but the DM has also allowed classes from Monte Cook's
Arcana Unearthed and from the Expanded Psionics Handbook and a smattering of other stuff (such as the Hexblade from
Unearthed Arcana). He has disallowed Monks and Sorcerers, but everything else from the
Player's Handbook is open, I think. I could be wrong about that. Races are the standard Dawnforge races.
Our game consists of a Night Elf Bard/Hexblade, an Ogre Spirit Adept, a Highlander Champion, a Lowlander Witch, a Saltblood Rogue, and a Tiefling Soulknife. It was really interesting trying to come up with ways of why our group is working together.
We're doing things a little differently - basically, the DM has house-ruled that because elves and gnomes technically come from a different "world", their magic works differently. So, for example, elven "bards" actually use the
Book of Eldritch Might II bard class, while humans and other races would use the bard from the
Player's Handbook (which he has renamed "minstrel"). He's also using spellpoints from
Unearthed Arcana for his wizards.
But, all that aside, the play is pretty much just like standard D&D. The world has a different feel to it, and I think as a DM that would be something you can concentrate on. To me, it feels a little more primal, a little more new... the racial animosities that are cliche in standard D&D are somewhat missing. Since the world is kind of new, the races haven't really had a chance yet to figure out whether they tolerate or despise each other yet. It's really kind of interesting.
I particularly enjoy the subtle political stuff happening between the night elves and the dawn elves. That's something else you could capitalize on if you wanted, I would think. I'm playing a night elf bard (with one level of hexblade) and there are usually some interesting consequences when our party (which doesn't currently include any other elves) runs into any dawn elves.
Another arena you have to work in is mystery - since the world is somewhat new, there are a lot of things that just aren't known yet. That's something fun for the players to have in front of them - the discovery of new things.
I kind of look at it, from a player's perspective, as a chance to "change" the way things turn out in the standard D&D mythos. For example, what if my character (or his descendants or whatever) could actually put a stop to the Cult of Lathail (the pre-Lolth type drow cult in Dawnforge) and bring the night elves and the dawn elves together for a common purpose, instead of letting the wounds between those two people get bigger? What if the Ogre Spirit Adept in our party were to succeed in forging an alliance between his people and the elves, or the dwarves? Those kinds of things are neat to think about, in my opinion.
If you have any specific questions, I can try to answer them for you.