Well, I have been playing quite a few shows since getting my Montage in July. Navigation, flexibility and sounds are great! The touchscreen, however, is difficult to see in some scenarios such as sunlight (both direct and indirect) or stage lighting. Is Yamaha thinking of making it possible to adjust contrast/brightness of the touchscreen?
The circuitry does not support changing the touchscreen brightness.
Although a BD6590MUV led driver IC for controlling the brightness of LCD screens is shown in the Montage circuit diagram, it's listed as "not installed".
A common low tech "solution" I've seen is use of a "tent" over the screen. You also have the option to do something non-official in adding an external LCD screen assuming you also add the right usb-to-hdmi (or vga or...) displaylink adapter. Lots to carry and position, but you can select a screen with brightness control where there is an acceptable range for outdoor use.
Here's an example "tent" (or sunscreen) you can buy:
Most would make one themselves out of common materials.
Current Yamaha Synthesizers: Montage Classic 7, Motif XF6, S90XS, MO6, EX5R