[giaur]

Would you go to settings page to change the 3d mode or rather use a shortcut?

For me personally.... it depends. Main problem with shortcut - keyboard is needed. All the rest of things that are needed to be done, can be done with mouse (I use wireless mouse). Even if I have keyboard connected, I still need to stand up and press 'y'. So this option in settings menu may be useful in some cases.Good example is Raspberry PI as media center. I usually don't want keyboard connected to it, wireless mouse is enough. The same if I have pc hidden behind my tv, configured to start xbmc automatically. There is no place and need to connect keyboard.

At the end... I don't think this option is unusable itself. But maybe you should place it somehwere in video settings available during playback? Next to aspect ratio and other video settings. Instead of main xbmc settings. 3D mode selected this way sholud be stored for each movie separately (if user choose settings as default for this movie) and stop playback = switch to 2D mode again (or, probably last used mode selected globally). When user starts the same movie next time, all video settings are loaded again (it works this way already) + selected previously 3D mode.
All of this would be custom settings to override auto detected 3d mode. Note that 3d auto detect functionality can detect 3d mode incorrectly in some cases, or even not detect as 3d at all (wrong file name, no 3d tag or wrong 3d tag inside mkv etc). So possibility to override it and store settings for each movie is not bad idea.

Of course, 'y' switch will be enough in most cases anyway (I thought you are going to remove manual switch completly). But I think my idea will be useful for people who want to use mouse only to control xbmc remotely. And for movies that can't be detected as 3D correctly. This option in xbmc settings is not very useful, because I need to stop playback, go to settings, set 3d mode and start playback again (or mimize playback). And it's still global setting, not for each movie.