Everything is still going great, with only one tiny snag to a smooth experience with Ubuntu 15.10 on the XPS 13. After a suspend/resume cycle, the wifi will fail to reconnect 4/5 times. To fix it, I've defined a small alias:
alias wifitoggle="nmcli r wifi off ; sleep 1 ; nmcli r wifi on" # toggle wifi off/on to re-init after sleep
So now, when I wake up the computer and the wifi doesn't reconnect, I can just type "wifitoggle" at the command prompt and in 4-5 seconds everything is reconnected (this is much faster than using the mouse to disconnect/reconnect).