I have had mixed experiences with using depth pre-pass. When I tried it a few times, I didn’t see any significant performance improvements on midrange to high end desktop GPUs. I'm not entirely sure why, but I suspect it was due to early Z rejection saving pixel shader invocations. Typically, I render my opaque meshes in front-to-back order.

To be fair, my experimentation was within the context of a CAD/CAM application rather than a game. The scenes were quite different from typical game environments, with minimal textures and very high-poly geometry.