With the release of vfsStream 0.8.0 the status is now beta instead of alpha as it was before. New features include a umask simulation which allows you to set a umask for vfsStream URLs which is then applied for new directories and files, except if you explicitly set the permissions of a file or directory using the vfsStream API. To be backward compatible and easier to use the default umask is 0000 - so if you are not interested in using this feature just don't use it and everything stays at it is.
Another new feature is the support of .. in URLs, provided via patch by Guislain Duthieuw, which means you can now have constructs like vfs://root/path/../otherpath which is mapped to vfs://root/otherpath. However, realpath() still doesn't work - there is no way to make this work with how realpath() is currently implemented in PHP itself.
Besides this two bugs have been fixed, one where it was impossible until now to access a child of a directory via the vfsStream API if the child name is contained in the parent's name. The other one was an incomplete error message when you tried to access non-existing files on the root level.