Hopefully a product like Roxul will become more popular when people realize its superiority; a little more marketing and placement wouldn't hurt.
Casey

Slag from steel furnaces was a common source of the base material.

With the decline in steel manufacture this ready source is now much smaller.

When the base material must be purpose made the costs end up about the same as fiberglass.

Glad I found it during my remodel - & utilized it widely
GC scratching head - but I got it, they installed - quite happy w/results

Jejvtr,

what is it about Roxul or mineral wool that you like it so much? I have also been thinking of it as well but remain undecided. Is it any harder to use than fiberglass?

Other than use as a fire-safing material in commercial projects the only advantage I am aware of is that mineral wool is denser than fiberglass (but similar to cellulose) so it is often considered a better sound absorber. However, in normal residential use the difference is not detectable.

If you want to upgrade your insulation from fiberglass batts at a reasonable cost, I would recommend sprayed dense-pack cellulose. If you are doing it yourself, mineral wool would have the advantage of easier installation.