Sometimes is difficult to paint textures in blender, as well as in photoshop/gimp, without a 3d reference. This times are when this tool comes very handy! Quick Projection allows you take a screenshot, open it in you image editor software, paint over it, and project it back into blender! This feature makes the process easier and it's pretty automated (that's why it's called quick hehe).
I used this method a lot of times for things like projecting a real face onto a 3d face (using Photoshop for distorting the real one to fit the model). With Quick Projection, you just work in the given angle and point of view each time, so for texturing a face, for example, you need to do it from several sides, one by one, the good thing is that you have all the great painting and texturing tools from your Image Editor to blend the parts where the current projection joins with the previous one.
Hope you like it and that you find it useful!! I think it's a great feature :D Thanks for watching ;)