I think my favorite feature is the fact that I can access my projects everywhere, even without bringing my computer.
When I'm at home, I can fiddle around on my Surface. When I get to work I can open my projects on my work computer when I have some spare time over and continue where I left off. Or if I get some ideas at work then I could quickly make some prototypes and save them to cloud, and access when I get back home.
For me this is by far the best feature as I don't like to carry around my Computer every day.
This is well worth the subscription for me, as I can play around with it anywhere.