On the ground I like my students to use checklists, Why? Simply because the majority of PPL's do not fly often enough to be able to memorise everything aswell as necessary.
The school I teach at has 5 different types and personally I very rarely use a checklist unless it's a new machine or I haven't flown it for a while.
I will admit that not using a check list has occasionally caused me to forget an item, but my pre-take off drills have always caught them before I get off the ground.
In the air ALL checks in a single crew machine MUST be done from memory. Foghorn, I would kick the backside of the instructor who wanted you to have your head down on downwind. Idiot!!
As Chuck and others have already said, nobody should just read a checklist. I've lost count of the number of times someone has said a check and thats all they've done, not actually actioned the item.
Checklists are vitally important, but only as an aide to memory NOT a replacement.
An old captain once showed me a great trick. At intervals during the cruise whilst we were chatting he would turn to me and ask "is there anything wrong with this picture??" Then we would have a look around for anything that may have been overlooked. Top system, usually we never found anything, but sometimes...