Getting back to the original question, I think that most professional pilots who regularly fly into and out of busy terminals know 'how the game is played'. At LHR, ORD, LAX, LGA and many other places, the traffic is run tight, because it has to be. Most pilots I've worked with over the years know from experience that you have to be ready when you are next to go near the runway. And for the most part, we are.
That said, I've also worked with the odd individual from time to time who taxied the airplane and followed ATC instructions as though he was the only airplane moving, by dragging the thing into position and being overly methodical when expedience was required. I even worked with one pilot who claimed that one should never taxi an airplane faster than a man can walk! Very frustrating to be a member of his crew.
On the other side of the coin, I can attest to the fact that pilots are often frustrated at some of the things we hear from ATC. For instance, calling for push and start clearance and being told to "standby", with no indication of how long a wait is to be expected. Or being number one at the runway hold point, anticipating a 'taxi to position' clearance when the arriving airplane is abeam us over the runway end, having everything done, and then either not hearing anything or being told to wait until the next airplane (who is 6 or 7 miles final) has landed.
In summation, I would ask every controller who issues a "Standby" response to a push or taxi or descent request to at least give us an idea when further clearance or instructions can be anticipated. It sure helps out at the pilot end.
As far as "being ready immediate take-off", to me it means just that. The checks are done, I'll get the thing promptly into position (runway conditions permitting) and the engines are ready to be spooled.