The Scanjet's driver is very basic yet deceptively difficult to use. For instance, rather than providing an eyedropper tool for one-click color balance, you have to navigate the tiny color wheel. In addition, it separates the settings for resolution and scaling, providing no feedback link between them, and HP does not provide an adequate description of what the various parameters affect.
HP's six-channel scanning definitely adds some dimension to colors. I scanned an intentionally oversaturated version of the Photodisc print test that had been printed on the HP Photosmart 8450 (three-channel image on the left, six-channel on the right). The yellows, reds, and greens are clearly better, as is the more subtle violet in the upper left corner.
Occasionally--just randomly enough to be frustrating--the six-channel scans produced this misregistration in the reds, which frequently went away with a rescan. It seems to happen more often with slides (shown here) than with reflective originals.
I was relatively impressed with the Scanjet G4050's color restoration capabilities. On the left is the plain scan of a difficult, tiny Minox slide. The restored version (right) has too much red but isn't bad overall.
Though HP's color restoration does a decent job, I still prefer the quality of the job done by the Epson Perfection V700 (right). The Epson's dust and scratch removal also did a far better job; in fact, the G4050 didn't seem to remove any dust and scratches from slides. Keep in mind that the Epson is twice the price of the HP, though.