you can have portrait mode (full screen, no glitches i think) on the following apps:
-pictures
-conversations (only in the menu for which u choose which conversation you want to view, not the actual texts/ims
-settings
-contacts
-email
-app manager
-file manager
-notes (but u cant type unless you have a portrait mode keyboard)
-sketch
thats all the pre installed apps, but therell probably be a lot more 3rd party apps that work!

HOW TO INSTALL
1. download "shortcutd" and "proximityd" from extras-devel using ur app manager (warning: devel apps might harm ur phone so be careful with what u download!)
2. install them
3. go to settings and scroll all the way to the bottom until you get to "ShortcutD" in the extras category.
4. click on it and configure either the proximity sensor or the camera shutter to trigger the action "Ctrl-shift-r (Enable rotation)
5. try it out and see what you think!