There are reports of belts failing, belt arms braking, and seats snapping in half with use as a treestand (not a saddle platform).
You can search on google and find many to read and make up your mind about how bombproof the stands are or are not.
I'd be hesitant to call the climbers "unsafe" but I wouldn't necessarily entrust my safety to a guy going by
@Nutterbuster or someone who doesn't "know anybody else" who has had a failure...telling you they're fine.
If you employ safe climbing practices and have plans in place to mitigate the dangers of a failure, then you should be fine.
Food for thought:
By always wearing a safety harness in elevated stands, checking equipment and exercising many accidents can be prevented.
www.louisianasportsman.com