Though I don't shoot many concerts anymore I did in years past with film. When scanning some of my slides and negatives many were very dark. Despite various editing programs, I was never happy with the results. Later I ran across a program that had better results out of the box than what I had done manually. It may not be what you are looking for but it will only take a little time to see if it brings out more detail in some of your images.
http://www.tommesani.com/AltaLux.html
OK, I'll probably be talking out my a** here, but from what I've read, one of the great thing about the Canon 40D is that it captures images in 14bit depth. Those two pictures that I posted earlier were almost totally dark when I took the pics and looked at them in my cameras display.
So, even though the image was nearly black to the eye, the 14 bit depth still provides significant resolution in terms of color gradation, since 14 bit provides such a large range of colors between pure black and pure white. This enables you to use some of the tools in photoshop, like the exposure, shadow, highlight, contrast, and lighten tools to 'save' an image. That's what I did with these two images. Not that they're good, but they actually were salvage from something that was literally almost black to the naked eye.
I guess what I'm driving at Flipp is that the software you link to seems to be pretty much similar to the highlight and shadow tools in Photoshop, if I'm not mistaken. I know that I've used those two tools to really lighten and add detail to the otherwise completely dark shadow areas of some of my images.
Regardless, thanks for the tips and I'd be curious to know others' takes on my comments above...whether or not you agree.