Would just like to add another voice to this. While the "front-end display" box may be helpful to me, as the person developing the design/architecture of my clients' sites, it's confusing and cluttering to the majority of the people creating content within the sites I maintain. Someone else mentioned an influx of "I'm getting an error message when I create content" emails--that's true, and I can't explain to many of them why in some cases there will always be an "error" message there even though there's nothing wrong with the site.
Many of my sites use a great many custom types managed by Toolset; telling clients that they need to tu it off manually for each type (and sometimes each session) isn't a solution.
Consider this a strong vote for an option to tu it off within the GUI...