Framerate problems with shaders on pretty powerful specs

[joevenzon]

That's correct, the high detail reflections are a new feature in the nightly build (previously selecting "high" would just do "low" and not tell you the difference). Based on the profiling data from your GPU, it's spending 35 ms in the deferred ambient pass, which is where the high detail reflections are computed, so that's definitely what's causing the slowness.