just wanted to add some comments now that I've tried a few trings and have started doing my own scanning.
first, I've found that foxit seems to do a better job at replacing colors (if selected) vs adobe reader. I've opened files in adobe that will not display at all only to open it in foxit & have it replaced the colors perfectly.
second, now that i've started scanning. I've found that running the images through fastone photo resizer for batch rotation & photo negative has been quite good. Fastone has a number of other batch operation options as well. I do play with the contrast & brightness as a straight up negative usually comes out as white text on grey background. By adjusting the brightness/contrast, I can get the background close to black.
Here's a sample of my color inversion using fastone:
I think there's some improvements to be had in terms of crsipness of the text..but i think that's a matter of playing with the focus/aperture/speed...i'm not sure i've found the optimal combination yet. Fastone does have a sharpen option, & in this example, i used +1 for sharpen.
Finally, just a note- i've found abbyy finereader doesn't seem to OCR as well with inverted color files (even when using its own color inversion option- which only makes the background grey..not black). So, i tend to use the non-negative images if i want to do OCR (for now). Perhaps a bit more testing will reveal that abby works fine with certain inverted color settings.