The Ubuntu MATE 15.04 version for Raspberry Pi 2 has been quite successful, and it seems to soon become the favorite OS for the small mini-PC after the official Raspbian OS.
The image is based on the regular Ubuntu armhf base and is optimized for the Raspberry Pi 2, one can comfortably use applications such as LibreOffice. Since, microSDHC I/O throughput is a bottleneck it is recommended to use a Class 10 microSDHC card for best performance.User needs a microSD card which is 4GB or greater to fit the image. The file system can be resized to occupy the unallocated space of the microSD card, similar to Raspbian.
The good news is the latest version of Ubuntu MATE v 15.10 is also coming to Raspberry Pi 2 and will be available for download on October 22, 2015.