@Brecht Van Lommel (brecht), eeh, that's indeed more complicated check than it originally looked like. It doesn't seem too much difficult to match the same behavior as Cycles, but the question is: is that tricky logic (iteration over psys and so) considered fine for viewport draw with Only Render enabled or we'd rather optimize viewport for speed instead?

I don't want to be rude or anything like that. But duplicating the same two code lines 6 times?

Regarding performance, if you were to implement this I would try to do most of it in object_handle_update, setting some kind of flag. That way it should be fast enough.