I bought the Lansky system last August after years of struggling to sharpen freehand and using pull-through carbide and ceramic sharpeners and Lansky Crock sticks. I like the consistent angle that the Lansky system gives my knives, but I agree with most of the points of criticism mentioned above: it's messy; the stones are too narrow and gouge easily, and it's uncomfortable to use for longer periods (I have yet to buy that little stand that the clamps mount onto). In addition, I have a few other problems with it.
For one, most of the knives I sharpen are pocket knives (SAK, Opinel, and Case), as well as a few Mora knives. All of my pocket knives have angled grinds up to the spine, with no flat parallel surfaces for the clamp to grip really securely. This means that the knife will tend to tilt to one side or the other if it's not clamped just right. Sometimes I will clamp at the very edge of the ricasso, but this is also risky because most of my SAK blades are asymmetrically ground in order to fit between the other tools in the knife.
The Lansky's pre-set angles, however, make it impossible to sharpen a Mora knife and maintain the single bevel of the Scandi grind; the grind angle is just too shallow for the Lansky system.
In addition, I'm having trouble with the beginning of the blade edge, just above the sharpening notch. The stones seem to wear down an area about a millimeter above the notch faster than the rest of the blade, leaving a tiny area that is almost concave rather than straight, and eventually giving the blade a "recurve" just above the ricasso.
My final criticism is the fact that the end and side surfaces of the stones are partially uncovered by the plastic handle. Inevitably, I'll be nearly finished sharpening a knife, when my attention (or hand) slips, and one of two things happens:
1. The stone drops off the knife blade, and I, without realizing this, begin the next stroke...and push the flat end surface of the stone right into the blade edge, rollin or flattening a section of the blade, or
2. At the end of a stroke, the stone drops off of the blade and the side surface of the stone hits the blade tip, flattening it.
Despite these criticisms, I have to say that the Lansky is the best investment in knife sharpening gear that I've made so far.