The reasoning it takes so long is that it works differently. It turns iron + air into steel + slag.
I'm not sure that really justifies it taking an entire minecraft day to produce 4 refined iron ingots in one of them, but on the other hand, by the time I have enough energy production (e.g. nuclear reactor(s) and/or Radioisotope Thermal Generators) to consider adding overclocker upgrades to my other machines, I should easily be able to build and run several blast furnaces in parallel. I might have been trying to build advanced solar panels too early, and I hadn't noticed the addition of the RTGs (which now that I look at their description on the Wiki seem more attractive than advanced solar panels).