Well, that was quick. A couple of days ago, Microsoft said that the Windows Technical Preview Build (which contains Cortana, continuum, new action center and more) would be available sometime next week.
Well, we were hit with a pleasant surprise as the Build is now available for download ahead of schedule!
If you are registered with Windows Insider Program, you can download and install now.
If not, you can always register, just go to Windows Insider Program
The Build is quite buggy though, so be warned, this is far from a finished product.
We are given the privilege of using it so as to give feedback to Microsoft, this OS isn't for your daily use, there is a list of known issues (and many more unknown issues which aren't listed) with this build, you can check out the list...
This list of known issues was provided by Microsoft, but these are just known issues, there are a lot of issues plaguing the build as I found out.
For one, my Yoga2Pro physical keyboard stopped working (though it took several reboots for it come back to normal).
There are still more issues being reported, so don't go downloading this build if you aren't ready to give feedback and report bugs.
You can read more about it from Microsoft Official Blog