OpenELEC is another well-regarded and capable media centre for the Raspberry Pi.
Like OSMC, OpenElec is also based on Kodi, an open source media player, so is similar in terms of its capabilities to play music, video and TV.
Installing OpenElec requires a little bit more manual work than OSMC. Start by browsing to the the Get OpenELEC page and finding the latest ARMv7 build, at present OpenELEC 5.0.3, and downloading the file labelled Diskimage.
Windows users should next follow the process for creating an operating system image outlined here, Linux users can follow the instructions here and MacOS X users should look here. Note if you're following the instructions for Linux then you'll want to download the tar file from the GetOpenELEC page, which is the one above the file labelled Diskimage.
OpenELEC seemed to work as well as OSMC at the core tasks expected of a media centre, playing the same video and audio files I tested on OSMC equally smoothly. However, navigating the menus in OpenELEC felt less jerky when using a mouse. Unlike for Raspbmc, I couldn't find any guides for how to play video from premium services such as Amazon Instant Video, but that doesn't mean it would necessarily be impossible.