I just installed the latest Windows 10 build in a VM, and I'm remarkably impressed. Cortana is working much better than expected, and I'm loving the new start menu. I'm planning on switching to Win10 full time for at least 6 months or so after release; been on OS X for many years, but I much prefer the direction MS is going, these days. It looks like they're going to be the first folks to really get a universal ecosystem across desktops, tablets, and phones; frankly, I'm surprised it wasn't Google.