Like all big companies your experience depends more on your group than the company as a whole. I've got a number of friends at MSFT in various tech roles, some have their own office as a developer, some are in a cube or open floor environment.
Note that the post you're replying to uses the past tense. The vast majority of my tenure at MSFT was in a private office, but that was over ten years ago. It is my understanding that things have changed since.