I have upgraded to Ubuntu 16.04 LTS from Ubuntu 14.04 LTS. There have been very few issues for what is essentially an engine swapout.
Wireless Lan not recognizing Old Connections
On my home wifi I hide the SSID. After the upgrade these connections do not seem to work. Or rather they worked for a while and then seemed to slowly stop working.
When I edit my hidden network connections, the old connections are there but the connect button is greyed out. I thought I had to go to my router, broadcast my SSID, get a connection, then re-hide my SSID. This did not work. It turns out there is a bug for hidden networks.
I also had to do this when first connecting in 14.04.
Gedit does not remember past edited files
This was new. I searched and found that it is an Ubuntu 16.04 bug. In gedit when I do N I get a new window, whereas before I would get a new tab on the same window, which I prefer.
Cannot Access Windows NT Share
This turned out to be a Windows issue. It seems my Windows server cannot support the enhanced security of the newer 14.04 and 16.04. I needed to drop the Ubuntu security in order to access my server. I added “client use spnego = no” to my smb.conf
For the most part, the Ubuntu 16.04 upgrade went extremely well. This is astounding as compared to a Windows upgrade, many of which I have had to repair after the fact. The Ubuntu 16.04 upgrade did not affect my dual boot.
I am thankful that I have chosen Ubuntu rather than stay on Windows. I still have a dual boot machine with Win7 on the other side.