Oh, I totally agree, the Unreal Engine is *great*. The Design Doc calls for both a single player "adventure" mode and a multiplayer mode. We've got 2 multiplayer gametypes close to complete, and we're building assets for the content as quickly as we can manage. The single player is a work in progress, and I'm actually writing out the story for it right now.
The gameplay experience is different depending on which team you are on, of course

If you're one of the flyers you are in third person view (toggle-able to any of 4 or 5 different cameras) and your primary weapons are to poop on yuor enemies. We have several levels of power (you know, just like taking a real dump, LOL) and we're working out the effects (graphically I mean) for each.
As a walker you're in an FPS view (each team has its own PlayerController class, assigned based on team membership) and will have access to a number of different weapons (in the design stage right now).
Some fun features that I've enjoyed the design process of include our PowerUps/PowerDOWNs system. The powerdowns basically either severely weaken you or they give you some awful attribute (tunnel vision, super-dee-duper jumping, or if you're a flyer, the loss of your ability to fly, etc.)
Hope to hear from you! Do you do any modeling/texturing/programming/Level Design or any of that?
Jason