I have a copy of "Once upon a time in mexico", it is a nice movie, but the extras are even more interesting.
There are various extras, like the "10 minuts film school", where Rodriguez explain how all the fx are done. It was a surprise for me learning that the gun effect (muzzle flashes, wall marks are done via CGI and not on the traditional way) i really did'nt notice it the first time... And for the steadicam side, it was nice to see that Rodriguez do almost all the camerawork, including the steadicam shots; in fact he can be seen two or three times wearing the vest and the arm. However, he claim to be a cheap movie-maker, but he says that, before start shooting "once..." he was talking with George Lucas, and Lucas showed him the advantages of HD digital cameras. Than he brought two HD cameras and start shooting the movie. Not so cheap... for us... Funny to see, is that when shooting a scene handheld, Rodriguez walk against a column into a corridor and broke the camera (or at least the optics)