We recently used housesimple to sell our house after seeing how poor a service you got from local estate agents for about four times the fee.
Whilst we didn't get many viewings, the ones we did receive had a genuine interest in our property due to the excellent descriptions, floor plans and photos provided by housesimple. We were able to sell our property for close to our asking price in a difficult housing market. Communications were very good and all queries were quickly dealt with.
If you are selling a property where you are able to conduct the viewings and where prospective buyers are likely to be internet savy then I don't understand why you would even consider a high street agent. At the time of selling, housesimple offered the most competitive rates of the internet-based agents and their service levels were excellent.