I just wondered how important you feel this is on a watch? I am finding myself considering this more and more important in my enjoyment and choice of a watch. I'm almost religiously "anti-quartz" and find myself fascinated by the movements in a mechanical watch - so much so I have started to learn more and more about them (which was once for me a completely secondary consideration).
Because I am so interested in this now I feel that I need to see it. I consider it a thing of real beauty and want to watch it in action. More often than not I find myself now attracted to a watch because of it's transparent caseback (takes all sorts right?)
For example, somebody posted up the Omega Speedmaster Sapphire Sandwich - I thought "Oh I want one of those" (pic below - not mine)
Then someone showed me the movement on the Zenith El Primero Pilot - it made me want one of those too (pic below - not mine)
How important is this to you guys?