I'm writing this blog post from Pidora 18, a build of Fedora Linux for the Raspberry Pi ARM computer.
I'm going to compare it to Raspbian, which is the usual OS that people install on their Raspberry Pi's.
As far as speed goes, Fedora 18 runs pretty well on this device. I haven't directly compared it side-by-side with Raspbian, but I haven't noticed any real annoying slow-downs at all. They've optimized Fedora 18 to run well and take full advantage of the floating point unit on the Pi, which previous versions of Fedora didn't do.
One huge plus with Fedora over Raspbian is that the NetworkManager applet comes installed and set up by default (as it does on all Fedora OS's). It was super easy to connect to my wifi network with it. Under Raspbian, there's only the
wpa_gui, and it doesn't work very well for me and I have to click the "Connect" button a dozen times before it finally connects. The NetworkManager applet is a huge improvement.
The Pidora distro comes with the XFCE desktop environment, as opposed to Raspbian's LXDE desktop (on my Raspbian, I had gone ahead and installed XFCE anyway). On my setup, audio was working how I want it to out-of-the-box. I have my Pi connected to a DVI monitor, using an HDMI to DVI adapter. In Raspbian, I had to uninstall Pulse and hack ALSA up to make it send audio out the analog jack instead of HDMI, so that I could connect it to some proper speakers. In Pidora, Pulse wasn't even installed by default, and ALSA already knew to send the audio through the analog jack.
I also managed to get Minecraft: Pi Edition to run on Pidora. I just needed to install
SDL, and fix the permissions on the vchiq device (using instructions I found on the Raspbian Quake3 page), and I was good to go.
The biggest downside to Pidora is that there is no RPMFusion for it. They rebuilt pretty much all of the standard Fedora packages for the ARMv6 architecture, but upstream Fedora doesn't include anything non-free, like MP3 support, and so Pidora doesn't have that available in their repos either. Raspbian is a better bet if you need MP3 and video codec support, unless you want to compile the software yourself.
I think I'll stick with Pidora though. It's a lot more familiar since I run Fedora on all my other computers, and pretty much everything about Fedora is exactly the same in Pidora.