I too almost found iCloud sync to be the be-all end-all solution of browser syncing, then I discovered that the same iCloud sync on Mac does NOT support Firefox

I too almost found iCloud sync to be the be-all end-all solution of browser syncing, then I discovered that the same iCloud sync on Mac does NOT support Firefox/Chrome - only Safari. I'm relying on Xbrowsersync for now but it's still not the optimal "everything everywhere" solution, as it does not support syncing to Safari (and from reading their website, its developer appears to be ideologically opposed to implementing it).