You can cast both halves and basically have an etb effect without actually having an etb effect
I've always been happy to let metagame forces shape eternal formats, but I do think that the possibility of bringing down the overall speed of the format would have been good
Do you attack and reduce the cost of your spells by three, and risk losing the ability to cast Sorceries at Instant Speed
They scale well, provide card advantage, and snowball effectively
Rooms were designed in such a way that you can use either half without wasting the other, so feel free to run out the Sauna on turn 5 and snipe something down with the Furnace later, or vice versa
The Halfling could really push casual tables around as a one-drop tapper of mana, even colorless, but it's very strong in Commander since so many things are randomly legendary without even needing a theme to toss it into