Hi Robert,
I passed using CardLayout and a single window open at any time (no MDI) - 100% for my user interface.
I have also seen lots of posts where people didn't even go to my level of complexity. They used a dialog box to get startup information, a dialog box to get booking details, and everything else was in a single frame.
Having a simple interface wont make you appear to be a rookie - in fact a well designed simple interface may be preferable to a more complex interface that uses technology for the sake of the technology
.
Regards, Andrew