One of the changes coming to you in PostGIS 2.2 are additional extensions. Two ones close to my heart are the address_standardizer (which was a separate project before, but folded into PostGIS in upcoming 2.2) and the SFCGAL extension for doing very advanced 3D stuff (was just an sql script in older versions, but made an extension in 2.2 and new functions added). We had a need to have address standardizer running on our Ubuntu box,
but since PostGIS 2.2 isn't released yet, you can't get it without some compiling. Luckily the steps are fairly trivial if you are already running PostGIS 2.1.
In this article, I'll walk thru just building and installing the address_standardizer extension from the PostGIS 2.2 code base. Though I'm doing this on Ubuntu,
the instructions are pretty much the same on any Linux, just replacing with your Linux package manager.