Wow, this thread really shows on of the most irritating things that I know as a professional pilot. When someone takes a step in to the flightdeck after landing saying something like: "that was a bit wiggly, wasn't it?"
A pilot for a serious airline would never do an intersection takeoff if he didn't know that he could make it safely. And what u described as hesitation of backtracking/lining up it is standard procedures, since the intersection distances are calculated from a different point than where the rapid exit taxiway centerline turns off the runway. We always have to make a slight "backtrack turn" to get the distance that is calculated.
The biggest time-saving is not won at the shorter taxi, but mostly from being able to get out before inbound traffic or other take-offs.
Now im gonna have to rush to work.
My first take off for the day will most certainly be an intersection-takeoff with my B738. (It always is at this base, pretty sure I don't need 3500meters)