I have a circa 2011 Mac Mini that is suuuper slow since (stupidly) upgrading to Sierra (10.12). I've been meaning to roll that back for a while, but am finally now getting around to doing that. My idea is to roll back as far as I can while still having iCloud work across my machines, but then I realized that I've probably 'upgraded' my Photos and iTunes libraries along the way. I suppose it's not a problem for iTunes as I can just update iTunes until it recognizes my current library, but I don't remember at what point it changed from iPhoto to Photos, and if the libraries are compatible (I imagine they are not). I was thinking of going back to 10.8, so I have iCloud and iMessages, but I'm not sure what to do about Photos/iPhoto. Anyone have any experience with this kind of downgrading?