We recently reno'd two bathrooms and I insisted on cast iron tubs for both. I wanted the solidity and long-term durability of cast iron as well as its heat-retentive abilities. Our floor was deemed structurally sound enough to support cast iron tubs, so no need to beef-up the sub-floor. The hardest part was getting the tubs up the stairs, and into the bathrooms (DH, his three brothers, and his good friend moved tub #1, but we hired our plumber's brothers-in-law, some big, beefy guys for tub #2--it was child's play for them!).

Our tubs are Toto 1525's, and we love them. I don't think they are selling tubs retail/for home use any more (I could be wrong, it's worth looking into). We couldn't go any bigger, in length or in width, so these were the perfect size for our space(s). Very comfortable and they look nice, too.

FWIW, our plumber had us install the tubs on the first layer of plywood sub-floor, then install the next layer (needed to have a certain thickness of plywood total?), the mud, and tile, so the tubs sit a little lower on/in the floor. Why he had us do this, I don't know, but I can see how it could make getting into/out of the tub easier with the "raised" floor outside the tub.

I have been researching tubs too and have gotten lots of different advice. The latest was that acrylic that has been reinforced with fiberglass underneath is the way to go. The tub can be deeper, there are more options for styling, and they are easy to clean (dishsoap!).

Does anyone have experience with American Standard Minimalist? I was considering the Kohler Archer, but it is not reinforced with fiberglass and it only has a one year warranty.

We just had an acrylic reinforced with fiberglass drop in installed. It is much deeper than our previous tub and I had also researched and found that an acrylic was suppose to be easier to clean, keep its shine longer and also last longer than a fiberglass. However, there are some fiberglass and some acrylic tubs that are thinner and cheaply made.