Like the technology used in Avatar, the 3D in Dark Void creates a depth of field sensation going into the screen, as opposed to the older 'gee-whiz' effect of stuff popping out. In Dark Void this works particularly well for in-flight sections of the game. The sensation of seeing in 3D helped me get a better spatial understanding of the environment. I found I wasn't so much thinking about weaving in and out of the ruined towers, spaceships, and buildings as just doing it. When the action shifted to more conventional man-to-man combat areas the 3D still looked nice but made little impact on playing the game.
The additional special effects kicked in by turning on PhysX are all just cosmetic touches but boy do they make an impact. Dark Void's jet pack puts the turbulence modelling to good use as each of the twin exhaust plumes swirls and realistically responds to momentum independently. It looked strikingly realistic as I pulled off aerial manoeuvres.
PhysX also provides a number of flashy weapon effects. Hitting an enemy with the disintegrator gun, for example, cause them to disperse in a wisp of particles on the wind. As nice as the console editions look, these effects give the PC version a real visual pop.
With both PhysX and 3D turned on, though, I found the combination distracting. The turbulent jet exhaust that had looked so good became a distraction as it didn't quite line up correctly with the rockets. All the particle effects from weapon fire still looked pretty but also noticeably increased my eyestrain. I'm not sure whether this was due to their taxing the system or my sight but either way it was uncomfortable.
For my money, I'd probably play the game through with the PhysX effects turned on and leave the 3D as an occasional thing to turn on and fly around a level that it works well with.
Dark Void is released for PC, Xbox 360 and PlayStation 3 on January 19. A demo is available now on 360 and PS3 but none is planned for PC.