Hi Jim,
I suppose that makes sense. The levels function is just inverting the input and the output numbers so mathematically it is probably the same as Photoshop "Invert". The next step is the tricky part, and the reason I use ColorNeg—applying curves to your now-inverted image to get the most pleasing tones. I have found that the ColorNeg inversion, whatever it is doing (and it is definitely not the same as a Photoshop "Invert" function) really nails tonal relationships, especially in highlights, which seem to get fudged by the scanner software, and makes those final curves adjustment very easy. I always found my scanned images to be a bit harsh when I let the scanner software have its way, but with ColorNeg I am very pleased.
I would say that the difference is as significant to me as when I switched to QuadTone Rip for printing instead of the standard Epson driver. I believe that software that gives you more control is a good thing.
I wouldn't suggest my approach for everyone, mainly because it requires more work and the software is not free. But based on the hundreds of photos I've now scanned and printed since discovering this technique, I am certain of the results.
Regards,
Dalton