I manage a decent size Google Adwords account. The Google adwords "strategist" they have call me is always pushing the Smart Bidding endlessly. So I try it on one campaign. Smart bidding increased the click cost from about $20 to $100. The one click converted but I get conversions on that campaign for about $60 so it was a disaster. Turned off that smart bidding and went back to my own eCpc bidding.