The Raytrace preview can be finicky at times, especially if your render settings are set to medium-to-high profiles; that is the bottleneck. I found the auto-update problematic in the Material Room where small changes would trigger it. It drastically interfered with the workflow. I predominantly render in Superfly and Cycles as long as the scene isn't too complicated and texture-heavy, which would impact the preview. But, to be honest, I don't depend on the preview window that often.