Hey Sam, I run ridewithgps.com and have been reaching into the guts of graphhopper to do interesting routing stuff as well. We just silently rolled out popularity based routing, where we used our database of 50mm rides to build a popularity graph which is used to add a popularity weight in routing decisions. Got a long pipeline of other projects coming out in the same space. Drop me a line if you ever want to yack about these things! cullen@ridewithgps.com