If you want to help the Ubuntu developers vet Mesa 11.2 (built against LLVM 3.8) for Ubuntu 16.04, there is the x-staging PPA with packages for the Xenial Xerus to replace its current default of Mesa 11.1. Mesa 11.2 was what I tested in yesterday's Ubuntu 16.04 Radeon performance article comparing it to fglrx on Ubuntu 14.04.4 LTS.
If you are curious about some Intel Linux graphics results with Mesa 11.2, I ran some quick tests with an Intel Haswell Core i7 ultrabook when doing an Ubuntu 16.04 LTS daily development ISO and then again when switching over to the x-staging PPA.
There isn't much change to these results, which are found via this OpenBenchmarking.org result file. Mesa 11.2 is still exposing OpenGL 3.3 for the Intel driver but at least the next Mesa release should fully take the Intel driver well into the GL4 world. Again, if you want to help test Mesa 11.2 on Ubuntu 16.04, try the the x-staging PPA. I'm still having some other Ubuntu 16.04 graphics (including NVIDIA/Nouveau) coming out in the next few days on Phoronix.