In the current version (2.0) in the Custom Content creation. It worked fine for the first one I created, but it seems to be degenerating with each try. Now, it shows me the title I entered, but back to the original text prompt.
With each Opt-In I create, it seems to save less and less text. First it saved the entire message (two lines of text), then just one line of text, now it only shows the original text prompt in the preview and live on the site.
I've found that if you write in the "Visual" editor, content is generally retained. Content generated in the "Text" editor is not retained at all.
Not sure why that is, but you should probably look into it.