The demo is fully feature-complete except that it contains the first six tracks, rather than the full 40. You can race against your friends' times on these tracks, whether they have the demo or full version, and your best times and medal will be carried over if you then buy the full version.
Demo now available
Source: Steam Community (opens in a new tab)
Build and release context
Steam update times within 24 hours of this post. Matching dates do not confirm which build it describes.
Build 6987350 · public branch
Steam updated · First observed