I've been playing around with it on M1 Max since the Alpha build with great results.

Here's some numbers from my latest benchmark run:

    "Junk Shop" demo using Cycles
    M1 Max (10 cores CPU / 32 cores GPU)

    Blender 3.0 (CPU) / 1:14.64 minutes
    Blender 3.1 (CPU) / 1:10.86 minutes (1.05x)
    Blender 3.1 (Metal GPU) / 0:44.16 minutes (1.68x)
    Blender 3.1 (Metal GPU+CPU) / 0:27.90 minutes (2.67x)

For a reference, RTX 3090 (OptiX) was 0:18.22