If you ever have a connection hiccup, or just plain lose service, you are returned to the main menu. With the DRM, you cannot play games offline, even in "single player" modes. This has happened multiple times where an Ubisoft authorization server has gone down, leaving legitimate players standing idle while those with pirated copies play happily.
Additionally, From Dust is currently missing graphics options, is extremely buggy, and is capped at 30fps, no matter what GPU you are running.
As of writing, Ubisoft has listened to the significant outcry about the game and will be sending out a patch in the next two weeks to remove the always-on DRM. Furthermore, they are offering a full refund to Steam users who purchased the game and "are dissatisfied."