Good stuff? How often should DI owners be running this?
Never? If you try to get it clean in one shot that pulls the deposits through the engine, you'll eventually ruin your cats because it comes off in larger chunks than if it were never accumulating in the first place. It can also jam up the piston rings so you burn more oil, and suffer from blowby and oil contamination.
Someone stating they did this to a non-DI engine for a long time, isn't contradictory because non-DI doesn't build up deposits anywhere near the same rate. It is not magic in a can. It's a short term solution that causes more long term problems than if you waited and did a proper intake/valve cleaning that does not push those chunks further into the engine.
If your auto manufacturer disagrees and prescribes using it, follow their recommendation. Are there any that recommend this? If you use it otherwise and cause engine problems, that SHOULD, rightfully void your warranty if still under one. I'm not stating it would make me happy that anyone suffers loss, it's not like it's a "you deserve it" lesson, not at all, just that gummy sludge is something you do not want to pull through a modern engine.