I watched the conference and was extremely impressed with what Windows 10 is capable of. What I was most interested in was their statement that 10 would be much better for gamers and they didn't disappoint. There is a game DVR with which you can record play from any game and save , share, or whatever else you want to do with it. It will also ship with the latest version of Direct X, DX 12 which is greatly improved in performance and capability over DX 11 and will not be made available to Windows 7 users. Owners of Xbox One will be able to stream their games to any device running Windows 10.
On the productivity side, Office will run on any Win 10 device, including phones, and there is a new piece of Hardware, the Surface Hub that will greatly facilitate on line and office meetings. Cortana is also fully integrated. Internet Explorer will still be a part of Windows 10 but there will be another browser option called Spartan which has been mentioned here before.
The most amazing thing is that there will be another new piece of hardware called the Holo Lens, a self contained headset computer. With it, you can make and view holographic images of anything and even more amazingly, save them and print them with a 3D printer.
Even though I won't use some of the new features, and probably won't buy the new hardware, I think Windows 10 is a huge leap forward for personal computing. It's no wonder they skipped the Windows 9 designation and went straight to 10. To me, this looks more like Windows 15 or at least, 12. I know I will be taking advantage of the free upgrade ASAP. (After making a system image of my 8.1 installation first of course. Just to be safe.)