Before you go to pull that tub out try this stuff first:
http://www.amazon.com/KRC-7-Bathroom-Cleaner-Restorer/d...
When I moved into this house I had the same problem. I was just about ready to take a sledgehammer to the two old nasty looking tubs that were here when I moved in and one of the contractors suggested I try that stuff before I got too carried away.
I am sure glad I did. This stuff works like magic. Made those two tubs look like brand new again after about an hours work.
KRC-7® ORIGINAL Bathroom Cleaner/Restorer
EMPLOYEE FAVORITE! Mary Burnett says, â€Genuinely easy to apply & removes all traces of scum and mildew in minutes with no fumes.†KRC-7® Original is a specially formulated, cleaner/restorer for bathroom use, and other areas where the following surfaces are found. It will safely and effectively remove soap scum, hard water stains, rust, mineral deposits, grease, and other contaminates from non-slip tubs, acrylic, ceramic, fiberglass, plastic, stainless, copper, brass, aluminum and glass surfaces. KRC-7 does not contain any bleach, abrasives, caustic, muriatic acid or petroleum distillates. KRC-7 is non-flammable and non-fuming.
http://www.berings.com/ProductDetail.cfm/go/MainCategory=6/pn=1/Product=KR7;jsessionid=7830f28eddc9630d305cCool.