I've got a Tinker Board, had it about a week (they were very briefly available on Amazon, actually, as soon as it shipped the page was taken down). I'm actually posting from it, was running some updates/etc. It is truly identical to the Pi form factor wise, I slapped it into a Pi case. I stuck an initial impressions on my blog, but more or less the 4 usb ports are through a hub, the gigabit ethernet is tied directly into the SoC so that makes it's networking amazingly better than the Pi. Wifi is snappy, especially when considering the "chip-tenna" it's using for an aerial.
Tinker OS is horribly unstable in my experience. The desktop crashes regularly and you have to reboot, or continue your work by switching to another terminal and living with the CLI. 0 graphic acceleration of any kind from what I can see, I have it hooked up to a 4k monitor, it appears to be upscaling a 1080p desktop and then putting a 4k mouse on top of it? The mouse is nice and crisp (and tiny) and everything else is kind of blurry. I've seen some noise concerning mainline patches for the Tinker board, hopefully those pan out. And hopefully someone decides to let us use the graphics subsystem properly.