I am pretty impressed with the casual release of the Microsoft Excel API, which I think is a pretty significant milestone for the world of APIs. One of the subtle elements of their API release that I think is worth noting, is the support flow they provide. Here is the actual text from the release blog post for the Excel API:
This is the most open, and casual I think I've seen Microsoft ever be. They are allowing the community to suggest edits to their API documentation using Github, encouraging the conversation on their own forum, as well as outside their ecosystem, on Stack Overflow.
I don't know. Maybe I'm reading too much into it. They just seem like they are getting better with each API they have released, and the Excel API release was much more casual, natural, and less rigid than I'm used to from Microsoft.
I can't speak to the technical design of each endpoint yet, as I haven't played with enough, but the overall experience of the Microsoft Office Dev Center is surprisingly modern, simple, and intuitive. There are still a lot of places where it feels like a knowledgebase and not an API community, but overall it exceeds what I'm used to from Microsoft when it comes to APIs.
I have to admit, I didn't hold out much hope for Microsoft when it came to catching up on cloud and APIs--something that is changing with each API they release.