>... It's not so much a "shock" as the need to relearn products people have been using effectively for over a decade
>... My customers mostly turn it off

vice versa, new potential customers are turned off because of the outdated GUI design. It's the question what you familar with. I think BIAB is so successful because of its content not because of its GUI. At the moment there is no other product which can compared with BIAB (GuitarPro is very much limited to guitar as instrument). Supposed there would be one with a more modern GUI design then I will go for it. There are some reviews out there where other people also complain about the GUI. I am not talking about the veterans who used BIAB over many years.

The problem is that PG music keeps adding many new features without changing much the GUI over the years. each GUI design started out with certain key concept. When you keep adding new feature without changing the GUI you will end up with a mismatch. For the veterans each new release means only a incremental learning process because they work with the product in such a long time. However, for newcomers this GUI is certainly not very intuitive and attractive.