According to the the Redditor, "Galak-Z currently is not stable on the PS4. Thus they had PCs with DS4s [Dualshock 4's] on the show floor running the game. I asked if this implied the PS4 controller works on PC, which he said 'yes it works as a regular USB controller'."
It's also believed that the DualShock 4's Touchpad functionality will also be able to be mapped like the touchpad of a laptop, though it wasn't confirmed. If true, the DualShock 4 could quickly become the optimal choice for PC gaming with a controller. Currently, a lot of gamers prefer the Xbox 360 controller for its ease and comfort, but with Microsoft confirming the Xbox One controller won't connect to PCs at launch, this could give the DualShock 4 an edge.
Following the post, fellow Redditor Halon50 posted a video verifying the functionality. Halon50 verified, "Yeah it works! For devs or enthusiasts who are interested in this stuff, it shows up on Win7 as a standard "Wireless Controller". The "Test Controller" properties shows 14 buttons and 3 axes of rotation. Here's a screenshot with the R2 and L2 buttons held halfway down so you can see them align with the "X-Rotation" and "Y-Rotation" bars."