So the name of the game is distraction managment.  Laptops to have knowledge of a rare rule is one thing.  Laptops to smurf off is something else. Opal has demonstrated on more than one occation that just having a the big two books is a huge boon, and can progress rather quickly.  I tend to DM from typed notes, but if need be, I can kill trees. :p.  I guess the real question is "will having device X keep you from paying attention?"  If the answer is "yes", then don't have it open at the table.

Phones can be tricky b/c people often use them as their sole means of conversation with friends and family, and that communication can't be dismissed.