I've been using Windows 10 as a daily driver for my desktop for quite some time now and really love it. I was curious about the best way to handle installing windows 10 on my Surface (when it comes) and still be eligible for the free upgrade when Windows 10 releases. I contacted Windows support and asked, "If I were to install and use Windows 10 preview on my Surface Pro, would I still be eligible for the free upgrade w/o Windows 8 being installed?". He simply answered, "Yes, you just activate it." Just in case anyone else was curious about this.