Two years ago I purchased AMD Radeon R9 270 graphics card and wrote about my experience in Fedora 20 and also experience in Fedora 21 (Rawhide at that time). I decided to post an update to this, especially after recent news of AMD and Ubuntu deprecating fglrx (catalyst) proprietary driver.
Overall, I have to say the opensource radeon driver made huge progress in the last two years, and I don’t regret my purchase at all. Quite the opposite, I believe I’ve made the best choice possible by picking AMD. Basically everything I complained about in the past got fixed or improved. The dynamic power management works without a glitch. None of the X11 rendering operations are slow anymore. Support for vendor fan speed profiles has been implemented, so my card it now completely silent. All desktop rendering glitches went away a long time ago. The regular daily desktop usage is completely perfect and issue free, and actually noticeably superior even to current intel driver (which was known for its stability and reliability). The intel driver regressed a lot in the last 6 months or so, when developers started rewriting some core parts, while radeon driver remains completely bug-free in my experience.
The situation is of course more interesting when it comes to gaming. There were large quality and performance leaps in the radeon driver. The driver gained support for OpenGL 4.1 and higher versions of OpenGL are expected to be implemented in the next months. That itself fixed a lot of games which refused to run before. Performance also went up significantly. On Fedora 20/21 I complained that Dota 2 ran with 5-10 FPS on low settings. Now I can play it on ultra settings with 80 FPS. Of course this is an extreme example, but it shows that things really improved a lot. It also helps that Fedora is very active in packaging latest graphics driver stack and we usually run on a very recent version of the driver (compared to e.g. Ubuntu, which is quite conservative in this).
I won’t claim that everything it top-notch, though. There are still a few games that don’t run or don’t run well enough. The performance is also not yet up to the catalyst speed. But for a person like me, who owns many indie titles from various bundles, plays a few selected AAA titles from time to time, and can reboot to Windows in the absolutely worst case, is the current situation actually very good. And it seems to be improving constantly. The radeon driver development team is very responsive and if you write a reasonable request or a bug report, they really try to implement it or fix it (for example they implemented GPU-based display scaling on my request).
If you are interested which titles run on my Radeon R9 270 and how well, I made a profile on opengamebenchmarks.org and benchmarked most of my Steam library. You can have a look at my benchmarked games.
As you can see, many even very graphics intensive games run quite well. For example Witcher 2 is infamous for how slow the Linux port is (it’s emulated by a proprietary wrapper similar to Wine), yet I can play it between 40-60 FPS depending on graphics detail. I was quite surprised.
If you are into gaming, I encourage you to submit your game benchmarks as well, so that we have an easy way to see how individual graphics and graphics vendors perform in games on Linux. I recently packaged voglperf and glxosd for Fedora, so it should be easy for your to install these benchmarking tools.
After considering all of this, I don’t really mind that AMD is deprecating catalyst. I understand that there are still use cases for catalyst, but most of the times the radeon driver is now a serious (and often better) alternative. If this means that AMD team will free up their hands from maintaining catalyst and will be able to put more people into radeon driver development (or the catalyst replacement which they plan to have on top of the opensource amdgpu kernel driver), it’s a good message for majority of Linux users.
Kparal's Fedora Blog 
After reading about the recent AMD kernel improvements, and your blog, I decided that I would also give this a try. I’m running Fedora 23, and have the same graphics card, an AMD Radeon R9 270X. However, the problem I’m having is that I cannot boot the Fedora kernel without specifying ‘nomodeset’ on the kernel command line (grub.cfg).
Are you using the ‘nomodeset’ or any other video/radeon kernel parameters in your configuration?
No, definitely I’m not. “Nomodeset” gives you a fallback driver, you’re not using the radeon driver. I wonder, have you been using catalyst on that system before? Maybe the uninstallation didn’t work as intended, and it’s still trying to find catalyst and failing. Try booting without “rhgb quiet” options and see whether you see any error printed by kernel. Or if the system boots but gdm doesn’t start up, connect using ssh and look at the journalctl logs. Everything should work out of the box. You can also download Fedora 23 Live image and boot it and verify whether there are any issues or not with a clean, unmodified system.
Good news: I found, and resolved the bug that was causing my issue.
Bad news (maybe for some?): it requires recompiling the kernel.
https://bugs.freedesktop.org/show_bug.cgi?id=76490
Comment 106 has an attachment which shows which file and additions that are required.