This was my first question, and there's no answer in their FAQ. Thank you for answering it.
I used a Samsung ARM Chromebook as my main laptop for many years, running Ubuntu. I only stopped two weeks ago when the keyboard finally broke (it did very well for how much it cost).
The biggest problem I had was that driver support didn't appear in the mainline kernel for years. When it finally did all work, it regressed regularly. I gave up bisecting the regressions to keep my own laptop running; I seemed to be the only one doing it.
Now I won't touch any ARM hardware (or any hardware, for that matter) that apparently supports Linux unless everything I need is already in mainline. Otherwise, by the time it lands (if it lands), it seems to be that there won't be enough of a user community left to keep it from regressing.
Thankfully, Pine64 has had a decent community these past two years so I'm not terribly afraid of the Pinebook getting left in the dust. But it's still a gamble.
I'm currently running Chromium with a few open tabs, SMTube, VS Code, and Hexchat without any problems.
Mine is set so that it boots from the internal 16gb eMMC into Ubuntu Xenial w/ i3wm. Then, I can either extend the storage or have it boot into Android, or any other distro, if I have an SD card inserted.
The Android build is well-refined with very few issues; just like the Pine64 SoC, Android is best for media-related use. The linux builds were rough at first, but most of the major issues have been fixed already by the community devs. They're also working on getting Linux on the mainline kernel, and to get 3D acceleration working.
It'll be a huge step for ARM if this device works out.