I've installed a few sets of these new injectors. They are easily identified by their index number of "11". They are improved injectors that were mainly designed due to the problems BMW has been having with the N63 engines -- which seem to be more sensitive to injector tolerances. According to BMW, you can run either the new or old style in the N54, but you can't mix/match them on the same engine.
Maybe my source was incorrect, but I was told the old part number was currently on back-order and that the new number was the same price. I'm assuming the new, improved parts are going to be the only option as soon as everyone runs out of the older "261" part number.