One thing to watch out for is that simple geometry will tell you that as you sharpen parts of the knife that are further from the clamping point, the angle of sharpening will change. To sharpen a very long knife, you may need to unclamp it and move it several times during sharpening. The system works extremely well for short knives, however. A number of hones are supplied, corresponding to different grits. Flat hones are used for plain blades.
Some rigs have a triangular hone available to sharpen serrated blades.
It also provides greater angle granularity than the rest. Although the price seems high, you should seriously consider this system. By all reports, the quality of the system is up to the price, it is very accurate, no multiple re-clampings need to be done. Typically the V-type sharpeners have ceramic sticks stuck into a plastic base at a preset angle. The system is easy to use, but obviously the angle is preset.