My current thoughts on Windows 10 build 9860. I've been running it since it was released.
In terms of functionality, it’s great. Start menu is powerful and customizable compared to it being just a v1 feature. Having Modern apps within the desktop is much appreciated as I am someone who valued the simplistic approach to their design but didn’t really enjoy the idea of having them full screen on a desktop box. Tablets, it makes sense but not for laptops/desktops.
In terms of stability, I’ve had it blue screen once. My recommendation is that you don’t load 3rd party drivers…keep the MS WHQL drivers from Microsoft Update. Once I removed the 3rd party drivers I haven’t had another BSOD.
For performance, it’s evident that there is debug code in it which takes its toll. You can notice a performance drop when opening apps and sometimes simple transitions. With that said, I use a lot of Hyper-V/VM’s and I haven’t had much of a problem at all in that regard. So it seems that anything that leverages API calls up above a certain level from the kernel will get hit, but if you’re VM heavy…it’s not a problem from my perspective.