Sorry, didn't mean to do a drive by and not answer your questions regarding salt. Waterbear nailed it. You could do a google search for pool calculator and find a nifty online tool that will tell you the effects of adding various amount of "stuff" to your pool, including salt.

Waterbear, thanks for clearing up the "softening" issue. Not being a chemist I was attempting to explain my own experiences with salt and "soft" was the only thing my feeble mind could come up with.