As I mentioned I generally do use curves on photo’s and have done so for a long long time.
The point really is that the GIMP levels is a lot easier to use for most people. It’s also present in a lot of pp package although the bit range of the output setting is as far as I am aware unique.
It too can produce excellent images all on it’s own. For instance on the shot on the demo that you linked to setting the left and right main sliders to each end of the histogram and then adjusting the centre slider would have very similar effect to the curve he shows. There is also the option of varying the position of the outer sliders and then adjusting the contrast. What the outer sliders are actually doing is setting the black and white points. The central contrast slider is adding a smooth curve There are a couple of tutorials here that show basic use
Sadly I can’t find the one that make use of auto levels to get colours approx. correct. Having numbers available and not just the sliders is useful too. A more advanced one that GIMP users may find interesting as well is this one that probably throws in some slight use of curves too. The initial use of levels helps with that.
