My Pi 2 B experience thus far.
Raspian (Debian Distro) runs really well actually, quite well. Web browsing is a little slow, but that aside it leaves me thinking that the Haiku and AROS ports are really going to have room to shine hear... assuming they tackle the video chip and can provide more than crappy Vesa support.
RetroPi is able to run 99% of the Sony games I have thrown at it with no or very very very minimal flaws. I had to tweak a few config files, but once done, I had the perfect PSX (and some) emulation machine.
OpenElec is a tiny linux distro for the Pi that boots into Kodi plays back video at 1080P with no problem. Something that can not be done in Raspian.
Quake 3 runs very very well, Dosbox runs great... I'm saying AROS and MorphOS need to be on here long with Haiku ASAP!!!