Rol, We were composing at about the same time. I didn't see you response even though you posted about 5 min before me. I was refering to the posting before yours that seems to call every one elses experience "dubious".
This probably won't be too popular of an opinion, but 9 times out of 10 it isn't worth cleaning the focussing screen. The dust (and scratches) generally won't really make it more difficult to focus and it certainly won't affect the image on the film. Sure, dust specks may be annoying but thats about all they generally are.