I was doing low-light theater work with the D700 using the DC105/2.0 and 85/1.8 lenses (wide open at around 1/15 and ISO 6400), and could not get consistent accurate focus with the stock Nikon B screen. So I looked for a split-image screen, and bought a Katz-Eye.
In tests with the Lens Align system, the Katz-Eye split-image screen consistently gives more accurate results than the stock Nikon B screen, and in actual low-light shooting, the split-image is faster to achieve focus, and more accurate.