I have been using one for the last couple of months.
The first few times using the slingshot was hard to touch my chest, I had to pull the bar down to get it to touch. It really helps take the stress off my shoulders and elbows. The slingshot helps keep my elbows tucked as well.
As far as increases go, my best raw bench is 315, I was able to work up to 365 with the slingshot on the second use.
Reverse band bench with slingshot went from 365 raw to 425 w/ SS.
Quality wise, it does appear to be well made and using quality material.