That's a good description of how this chuck works. It essentially makes your Festool drill into a screw gun, which makes it 5 drills in one if you have the right angle and eccentric chucks already.
It's good for drywall, especially if you're just patching. I think if you're hanging a whole bunch of drywall, you might want to get a dedicated screw gun but you certainly wouldn't have to. I've used it hanging a lot of drywall before. I admit that I'm not a screw gun expert so maybe an expert would go faster with a dedicated screw gun.
It's also good for any task where you want all the screws to be set at the same depth, like a deck.
You can also back screws out with it without having to change the depth setting.
Tom