It seems like a reasonable metric. If someone only uses Photoshop and Photoshop doesn't work on a given OS, the OS is probably useless to that person. It might

It seems like a reasonable metric. If someone only uses Photoshop and Photoshop doesn't work on a given OS, the OS is probably useless to that person. It might still be fine for other people who don't care quite so much about Photoshop. In my case it's a large number of apps that all use the same broken API because they are made from the same framework.