I use a DM screen. I *rarely* use it a reference though, I use it to obscure vision from my notes, books, and rolls.
Since I do not use any Tablet or Laptop, I rely on my old traditional composition notebooks, graph paper, mini spiral notepad, and spiral notebook. So all my checks, monsters, encounters, etc...are all listed and could be potentially seen by the players whether they are trying to peek or not.
I also lay the monster manual or NPC sheets out behind the screen. Without it, the players would see the enemies and their stats pretty easy.
Lastly, I like having my rolls hidden. This way I can fudge my rolls, usually to keep from TPK'ing the party if I failed to design an encounter properly. I have fudge things in favor of the enemies, but that is more rare. Basically I feel by hiding the dice I can keep the game more interesting.
The only thing I could see myself easily changing is rolling in the open since I fudge rolls incredibly rarely. But I would still like a screen to hide my physical notes and whatnot.