This Add On works by taking whatever you have as the Field Label and hiding it, then using that for the placeholder text….you simply have to add a Class to the input on the Advanced tab.
SO it works, but isn't ideal in the event that you want your placeholder text to be different from your label, and/or you don't want the label hidden. It's a workaround at best for a feature that Gravity Forms SHOULD have built-in and that GF users have been requesting for a long, long time.
Until GF adds in a option to easily add placeholder text to all input fields, I hope the developers of this Add On will consider adding the ability to specify different placeholder text from the label, and the option to not hide the label.
But if all you need is to have the label appear inside of the input field as placeholder text then this works very well.