I have - it's where the payment share scheme of my critique comes from:

As you see, they offer discounts in exchange for a share of any bitcoin mined.

for almost the same price as their 'heat with benefits' I could buy a prebuilt heater case + miner like @Luis. For $55 more I can get a thermometer to adjust using an app & degrees rather than wattage. And I wouldn't have to share my mined bitcoin with anyone else to do it either.