I tried vibram once and wasn't impressed at all. Had the boots for a week and sold them. Nothing beats studded felt soles on rivers with slippery rocks.
Good friend of mine was recently down on the Holston River in Tennessee...he was texting me fishing reports and pics and told me that the river was very slippery and he fell in a few times already and bruised his knees. I asked him what his boots were and he said vibram. I told him to visit the local fly shop and buy some felt soles with cleats. Later that day he texted me and couldn't thank me enough.
I only use my lug sole boots where slippery rocks are not involved.