I'm aware. I've tried to use it before, but the FPS hit I took from so many dwarves trying to path through all the mining areas, and not just the miners/stone haulers, has previously made such forts non-viable, so when the trees became multi tile (and thus viable as a fuel source for mass steel production), I switched over to the surface.
Maybe my next fortress I'll give magma smelting with minecart-based hauling a try, since my new computer is holding up so well.
I've got a cart-based magma reservoir in my current fort. It takes a while to set up, but works like a charm once complete. (It took until near the start of year 3, but I had multiple projects going, and the largest time waster was re-designating channels because just digging channels straight down kept having miners climb out when they got thirsty after just 3 z-levels, forcing me to manually re-designate a new dig and wall construction for water-tight channeling for the aquifer-to-magma-sea water pipe for the waterwheels. Just making the powerplant at Z110 and vertical axles all the way down would have been easier...) Magma pistons are also viable, but probably take even more time to complete, considering it involves more excavation.
When I want magma forges in a hurry, though, I just build a second fort on the magma pipe. If you just dig a drop-chute, you can chuck food via cart down into the deeps, and once you build a cart route back up, can easily ship metal goods back up to the surface. (And such a drop and return, once connected to a magma source, can easily be altered into a magmacart track...)