"Ready for immediate takeoff" just sounds a bit arrogant over here - ie "I'm in a hurry, I want to go NOW".
Think I can second that. The few times I heard mention of an "immediate take-off", (or was it even a "rolling take-off"?) it was when listening curiously - and slightly outside legal - to one major airport round here, and it was TOWER inquiring "bluefish niner four zulu, are you ready for an immediate?" when they saw occasion. Never heard the "immediate" initiated by a pilot.
I do not fly at controlled a/d's myself, but was always taught we should consider controllers as people working for us - and in other contexts I was taught to be polite versus people working for me, especially if they have any degree of authority.
Slightly off-topic: hearing how the big people do it, and taking their example where applicable, has been a great inspiration to my R/T.