The Criterion Channel rotates many of their library titles monthly and has sections in the app dedicated to what has recently begun streaming and what will be leaving the service soon. Some titles, such as All That Jazz, have not been available to stream anywhere and are only available on Blu-Ray/DVD. Others, like the Criterion’s edition of The Third Man, are out of print and only available on the Criterion Channel (and usually for a very limited time).
It is by far my favorite streaming service. I highly recommend it.
EDIT: Some but not all of the bonus features are included on the streaming service. Which ones and when they are offered vary.