hardiback or durarock for basement floor
i just used durarock in my bathroom. it was easy enough to cut. don't bother with one of the special scoring knives...just use a utility knife, and replace the blade a little more frequently than you would with dry wall.
as far as a basement floor goes, it would be a lot cheaper to use a leveling compound over the existing cement. and the cement board is not going to "level" out the floor, although it will provide a more uniform/smooth surface. but the combination of a leveling compound and thinset should be enough to overcome any uneven cement in your basement,....i would think.