So unless I want to use Siri on my computer (I don't) or tighter integration with iPhones (which I don't use), this update brings mostly nothing of significance.
For photos, it even recompresses the local files when space gets low and restores higher qualities from the cloud when you have more space.
As for Safari 10.0 not working on all but the last version OS versions, thankfully there's a choice - Chrome and Firefox.