We played the game for the better part of a day on one map called Eucadia, which was big on a Resistance: Fall of Man scale. It was an island, surrounded by water on all sides, but had towns, twisting roads, valleys, mountains, all kinds of stuff, and copious flying room overhead for dogfights aplenty.
We played a number of different game variants - Deathmatch, Team Deathmatch, CTF, Zones (which is a bit like Nodes in Resistance or 3 Plots in Halo 2, ) all of which had different configurations of on-foot or vehicular play.
On a whole, the game was surprisingly fun. Running on foot, grabbing a flamethrower and dusting a tango before hopping into a Warhawk and blasting away like a next-gen Luke Skywalker was, simply put, just plain bad ass.
Flying the Warhawks, you can use the Sixaxis motion-control in two modes, normal and pro. We tried both, pro is much harder as there are more nuanced moves you can pull off. You can also opt to use the standard analog controls as well. There was a pretty steep learning curve for the Sixaxis - you could tell when you went head to head against someone who was just learning the controls because they flew like a drunken crop-duster from Arkansas.
Presentation-wise, we had close to 30 people playing at once and had full voice-chat support and there was nary a hitch in framerate. The graphics are clean, there's a ton of customization options for both your soldier and Warhawk, and the environments are really fun to navigate. Plus, the tanks move at a good clip and the jeeps control well. So far, Warhawk is shaping up to join MotorStorm and Virtua Fighter 5 on the PS3's fledgling "must-have" list.