After having problems with bumblebee and now using nvidia-prime, I am still running to into problems.
The first issue is that the ability to switch between NVIDIA and Intel drivers is nowhere to be seen in NVIDIA settings. Note that there is no mention of intel when switching via sudo prime-select intel: http://paste.ubuntu.com/12916536/. Secondly there are two issues at startup -- Ubuntu does not pass beyond Plymouth unless nomodeset is requested and when it does boot up, lightdm loops when I try to log in unless I stop it, switch to intel and start it again.
Ubuntu 15.10, HD 4000, GT 635M
Thanks for any help.