I am. I'd say the value is small because there is no heat issues - but it does help by eliminating the scratches the plastic lens seems to accumulate quickly. And it is rather inexpensive as well. For this reason I would recommend the mineral glass and shy away from the sapphire.
Geoff, I don't know how a lens that big could fit in there. Perhaps they changed the size of the lens? I have the "old" model lights (not rated for the Newbeam). 23mm did NOT fit. I determined size by measuring the original lens carefully before ordering, although my tape measure only had increments of one mm. I ordered a bit of a spread and tried them.
Can someone measure the lens in their new model? It does look like Frei&Borel carries a 25.1mm which should be darn close.
So my optimal Mini-mag is Mini-mag + Newbeam + Kroll tailcap + 22.5mm mineral glass lens.
-john