I could not get any of the video or erase keys to start the GUI.
I just tested that feature on my S100. It works but maybe not how you expected. Once enabled via the CHDK setup menu, pressing the video or erase key will toggle the GUI on/off when you are in <ALT> mode. You still need to enter <ALT> normally. And you should not use the same key for the GUI toggle that you use for entering <ALT>.
For the test builds why not have new Gui as the default and embed the old one in it?
That was kind of a political decision on my part. Adding new features to CHDK is done carefully these days - as it should be. I wanted to point out that the UI GUI does not change anything about how standard CHDK works. Having said that, I always hoped it would be decided to enable it by default and let users turn it off if they found it confusing or otherwise did not like it.
There are other things to work on as well (see my second post in this thread) and new bugs to iron out. For example, the script name display in the lower left hand corner currently flows past the <ALT> symbol.
