The beta just landed this week, August 2nd 2016, with the Windows 10 Anniversary update. Some older computers aren't offered the update immediately, but you can

The beta just landed this week, August 2nd 2016, with the Windows 10 Anniversary update. Some older computers aren't offered the update immediately, but you can download the update or a full ISO for a clean install which contains the update. Installation went off without a hitch and the essentials all work perfectly (things like sed, grep, awk, wget, curl, etc.) as did installing some basic packages like git and sqlite with apt-get. It hasn't crashed on me yet, but I've only used it very lightly to test those few things that I mentioned. I'm going to withhold judgement until it's out of beta but so far it looks stellar.