There is a noticeable difference when I am playing with a cue that is not mine. Off the wall or someone elses $1000 custom, doesn't matter. If I don't know the particular playing characteristics of the cue in my hand, I will not be able to play as well as with my own cue.
Definitely. Athough, once in a while I find a cue that plays better than mine and I still play bad.

Best,
Mike