Some gunk came out, but nowhere near as much as some of other reviewers' pictures.
The smell of this stuff is absolutely toxic. Like hospital grade drain cleaner. Be sure you have good ventilation in your bathroom before use, as you have to run the jets for 15 minutes.
Washing it all off wasn't a picnic either. I did two full bath rinses and wiped the tub. The bathroom still had a noticeable stink of this stuff.