I see it as an overly complicated way of trying to apply containerization concepts to a base OS via transactions. It's really hard to use OSTree on new projects or get existing distros like Debian to work with OSTree. I think the update process, while in theory should be better, ends up being a black box of will it/won't it frustration for end users.

Finally, OSTree is mainly a Red Hat thing and is built for their needs (CoreOS). They could pull the rug on it in the sense that what you build today using it may not work tomorrow if Red Hat needs OSTree to function differently. Which is their perogrative, as they are the primary contributors to it.