Right now you can get all the Substance tools (including Stager, extra content and Modeler when it comes out) for $25/month. That's $5 more than the texturing tools only. As for the app itself, Stager is a tool for virtual photography. It has a pretty wide range of use cases, from simple portfolio renders, to product…
Stager already outputs Object and material masks + depth + denoised render + raw render if you output to a PSD file. This only works with the CPU mode right now though but will be available with the GPU render in the next update. Scattering system, we'd love to get to. You can scatter stuff in the geometry graph of…