I bought it, and never use it... I own an Epson V700 that I use with Vuescan to scan 6x7 film, and after a long learning process I started to get decent results but still had difficulty with certain images. So after finding ColorNeg I thought it may be a step in the direction of improvement, yet it seems to be a step backwards, and it was the most unintuitive program I have ever used. I'm not a big fan of sliders and presets and am quite happy to enter values manually, but the interface lacked instant previews and live updating of newly entered values, and also seemed to change values after entering and accepting them.
Maybe with a bit more time and a lot of effort I could have gotten somewhere with the program, but scanning film is a lengthy process in itself and the last thing I wanted to be do be doing is mathematics and struggling with a very difficult interface experience.