While trying out my brand new Asus R9 390 with Star Trek Online I was getting extremely low frame rates while in ground content, lower even than with the R9 380 that this new card replaced.
By low I mean sub-15 fps even with all graphical settings turned down, yes it's at 1440p but that should be the least of the issues.
While playing in windowed mode with GPU-Z running to monitor GPU core clock speeds. I noticed that while on ground the GPU core speed never went above 400 mhz. Bear in mind the 3D clocks of this GPU are 1050 Mhz normally.
Unlike some others it hasn't crashed, just the clocks running at low speeds, like it reuses to go into 3d mode.
I've tried this using both DX11 and DX9 modes, with both Crimson drivers, most recent hotfix ones, and even the last known Catalyst.
My system Specs for those wondering:
Asus Radeon R9 390 Strix 8gb OC
16 GB Kingston Hyper-x PC-1600
Samsung 840 EVO 500 GB SSD
Asus PB258Q 25" 2560X1440 monitor
Windows 10 Home 64 bit