I noticed that set visible for tab 1 in the editor always saves as false so whenever the panel is opened in our app the widgets on tab 1 are hidden and the framewindow looks blank untill it is clicked on. This can easily be fixed by loading the .Layout into a text editor after saving from the layout file. But it is still an annoyance. Just thought I'd mention it.
Here's a pic of the tabbed UI in action
