Here's some screen grabs as I was getting ready to test disk insertion/removal under GSOS. Note that everything you see may or may not change by the time you get your CFFA3000, but here is a snapshot of development at one particular moment in time:
First, the main menu. You get here by a CDA on the GS, or by invoking the firmware, or by hitting 'M' on power-on. This gives you a nice overview of the firmware revision (development drop 114 is already old), the physical slot the CFFA3000 is in, what memory devices you have plugged in, and how many virtual disks are currently being hosted:
Next, the Status screen. This shows you exactly what images are where, and there are some options to un-insert the disk images and get ready to insert other ones.
And finally, the choose images screen. The left side shows the images that are on your media, and the right side shows what images are hosted. You use the arrow keys to move left/right between the panels, and tab switches you between CF/USB (left side) or SmartPort/Disk II (right side). You can add images (by hitting Return on an image on the left side) or remove images (by hitting Delete on an image from the right side). You can see there are times when you get a view of the entire long name, and cases where it's shortened to the 8.3 filename - mostly because of screen size limitations of 40 columns:
There's still a lot of work going on to synchronize the "actual" state of the image hosting (Status screen) and the "desired" state of image hosting (Choose images screen). As I said, this area is where a lot of change will still be taking place before the final release is ready. It's perfectly useable now, but there are always improvements that can be made to make it easier to use and understand.