My desktop has an R9 Nano (using a GCN 1.2 aka Fiji core) from 2015. I've been using AMDGPU since Linux 4.5 and couldn't be happier. Everything that I do works as intended, from desktop compositing to Minecraft to Steam games (no AAA stuff, but e.g. Cities Skylines and Portal 2 work flawlessly).
(Haven't tested OpenCL, multi-monitor and HDMI audio, though.)
So IMO, if your GPU is supported by the AMDGPU driver, by all means give it a try.
> no AAA stuff, but e.g. Cities Skylines and Portal 2 work flawlessly
Do you get playable frame rates? Cities: Skylines pretty quickly falls to 20-30 fps even with a recent Nvidia card with closed Windows drivers, wondering how is the experience with AMDGPU.
Not sure how well the APU's are supported on amdgpu yet, however, I used the amdgpu driver with a RX560 and RX570, in both cases it was incredibly stable and a simple matter of telling the mkinitcpio config to use the amdgpu module and not the radeon module when building the initramfs.
KMS should be supported out of the box with amdgpu.
I am using an AMD APU A8-7600 with X11 and XFCE desktop. Am also using KMS for booting. Only very sometimes I paly a game. I do watch a lot of videos.
Any gotchas? Is it usable yet? And I am not misunderstanding things, right? :)