Our requirements are currently listed on our Steam page at http://store.steampowered.com/app/438100/VRChat/.
We currently have the following minimum requirements to run VRChat and only support Windows PC at this time.
OS: Windows 7, Windows 8.1, Windows 10
Processor: Intel® i5-4590 / AMD FX 8350 equivalent or greater
Memory: 4 GB RAM
Graphics: NVIDIA GeForce® GTX 970 / AMD Radeon™ R9 290 equivalent or greater
DirectX: Version 11
Network: Broadband Internet connection (25mbit+ preferred)
Storage: 1 GB available space
As far as VR headsets go, we should work with any headset that works with Steam VR. The headsets confirmed to work with VRChat are Oculus Rift and HTC Vive. We work with and without the Rift and Vive motion controllers.