I bought a pair of the Simm's boots with Vibram soles about 2 years ago when my studded felt boots had seen better days. I added 8 star cleats to each boot in a pattern that made sense to me. IMHO nothing can beat studded felt for overall stability and safety in the kind of fishing that I do in streams and rivers. Needless to say, I have been frustrated by the new product. Obviously, a big factor is the kind of bottom you find in the stream. In streams with a lot a flat stones like slate or a gravel bottom, the boots seem to work fine. But, in a stream full of round cobble stones or bowling balls, they are not good. If you can place you foot on a relatively flat surface, the cleats will tend to bite in. But, invariably, I will put my weight on the outside edge of the sole where there is no cleats as I step onto a slippery, angled rock and it isn't pretty.