I was really hoping that Microsoft would take the Apple approach with Windows 10, I was getting tired of spending $120 for each Pro license.
I loaded the W10 preview on my old testing laptop (an old dual-core Pentium T4400 with a JMicron 64GB SSD) and it has been a really good experience. It's surprisingly snappy for a six year old CPU and terribly SSD. Not all the DX libraries are part of the preview, so some games crash when looking for certain DLLs, but manually installing DX packages and running in compatibility mode usually corrects it. Other than the DX issues, it feels really good.
I still think they have work to do to get rid of the Metro influences on certain Control Panel items. It's jarring to go from a familiar desktop environment to a full screen, overly simplistic, Metro "toggle switch" window, depending upon which setting you're trying to change. Desktop mode should have ALL desktop menus and interfaces. Metro mode should be all Metro style.
It's a really good move to try to get the entire 7/8 crowd on board. You can tell that they are trying to reach out to "nerds" by talking about game performance and Xbone streaming, but what they've announced so far isn't really very impressive. DX12 will be great, but the other features they need to work on.
1. Stream Xbone to PC? No thanks - give me the ability to stream ANYTHING from any W10 PC to another W10 PC or device. Not just games, but anything from the frame buffer. Also, multiple streams.
2. The DVR function only for games? Apply it to all frame buffer activity and let me adjust the recording time. (My guess is that you can probably reg hack it to do more than 30 seconds.)
3. Xbox Live integration... I'm guessing that I'll have to create an account in order to utilize any and all interesting features. Microsoft is likely banking on users creating Microsoft accounts in order to take advantage of all the live-tile and cloud integration. They already have a great combo deal ($99/yr) for Xbox Live, Office 365, Cloud storage, etc... so I'm guessing they're going to push that harder than ever to help justify the "free" experience.
As long as the free version isn't gimped, I'll probably upgrade most of my PCs. Of course, they haven't announced hardware requirements yet. Based on my experience, W10 will run really well (better than 8) on old hardware.