While the Radeon R9 290 has been out more than a half-year, the open-source support is still poor. In fact, when running the latest open-source code there still isn't hardware acceleration by default, and with distributions like Ubuntu 14.04 LTS there's only mode-setting support without any 2D/3D hardware acceleration. In my most recent R9 290 open-source testing, I installed Ubuntu 14.04 x86_64, then installed the Linux 3.14 kernel (and later, Linux 3.15 Git), followed by using the Oibaf PPA for Mesa 10.2-devel and xf86-video-ati Git.
When booting the system with the recent Linux kernel versions, Mesa 10.2-devel, and the xf86-video-ati Git DDX, hardware acceleration is not enabled by default... However, kernel mode-setting and everything else worked fine (including the mode-setting of a dual-link DVI display at 2560 x 1600). So next I tried setting Option "NoAccel" "0" within the xorg.conf configuration to enable the hardware acceleration support. Unfortunately, that didn't go well.
When trying the Linux 3.13 kernel with the updated user-space there was an error due to the ring test failing. Mode-setting hadn't even worked right in this case, hence remoting into the system.
When trying out the Linux 3.14 kernel with hardware acceleration attempted, there were a ton of GPU faults detected...
Lastly, when moving to the Linux 3.15 Git kernel, there were still many GPU fault issues on Ubuntu 14.04 -- this was with the mainline kernel archive package, the Oibaf Mesa 10.2-devel and xf86-video-ati Git packages, and also ensuring all the latest Radeon microcode was installed. When re-enabling NoAccel, the mode-setting continued to work fine, but when trying to get hardware acceleration to work for the Radeon R9 290 it was still a mess and wouldn't even mode-set. So for those wondering about the Radeon R9 290 series Linux support, you're likely best off with Catalyst. If anyone has better experiences please advise through the forums. I'll keep checking back on the open-source status of AMD's new graphics hardware.