I upgraded the Ubuntu kernel to 3.16.32-lowlatency and Debian to 3.19.3 built from source with pre-emptive kernel option. I also somewhat cleaned up the start-up scripts on Debian.
This fixed a stuttering video problem on Ubuntu when viewing a Youtube video via Firefox over X2Go.
On Debian, it significantly reduced the time for the Maté desktop to come up.
Let me know if I broke anything in the process.
One thing I did learn of interest, a current 3.19.3 NFS version 4 client will interoperate properly with a 2.6.26 NFS version 4 server if the current nfs-utils are installed and everything is configured properly.