I have been using the Lanksy 4 stone diamond sharpening system for 5-6 years, and I have been very pleased with it. It is easy to use, the soft grip clamp is good, and the guide holes works like a charm. I do belive that even my mom can use the lansky sharpening system. The only downside that i experience, is that your arm gets sore after a few knives, and the final stones are alittle coarse.
The build quality is good, and the rods and nuts seems to be in good quality. After 5 years of use, the diamond version stills looks like brand new.
Coarser or finer stones can be ordered from Lansky´s webpage, and there are many different options.
Just a good tip
After you are done sharpening with the Lanksy system, its a good idea to hone your knife on a piece of leather using a polishing paste. It will really make a difference, and only takes like 10 strokes on each side. Place the leather on a flat surface, and pull the knife backwards (dont cut the leather) with the edge on the leather in a 20-25 degree angle, and you are good to go.
Its not the most expensive system, and its wery well known around the world. The stones comes in a variety of sizes. Can be bought in most hunting stores. Easy to use, and easy to get knives very sharp!