Specialized was one of many vendors at RTR offering demos. They took care of my bicycle when I rode the S-Works. I had no desire to ride any other bicycle and didn't want to regress to a demo with mechanical shifting. The first day was chosen because the climbs were less stringent than the second and third days.
This was a fantastic option for riding a a Roubaix with an SL3 frame under conditions that would allow an intelligent comparison between my SL2 and a new SL3.
I was quite happy to have the 30 tooth sprocket on a steep climb over McClure Pass.
When I rode the Cape Argus Cycle tour in Cape Town South Africa earlier this year I rode a Giant rental bicycle. I had no trouble adapting to the Giant and felt it was a very good choice for a rental. I had no regrets. From this experience, I knew a demo on a Roubaix S-Works would not cause remorse.