Mist was introduced on July 9th 2016. It was labelled not as version 1.0 or 0.1 but as 0.8. This is because it continued using the version number of the Ethereum Wallet.
https://github.com/ethereum/mist/releases/tag/0.8.0 links to the release and also explains the thinking behind the Mist/browser concept.
You can think of Mist as the browser for decentralized apps. Like what Firefox or Google Chrome are for the Web 2.0, the Mist Browser will be for the Web 3.0.
What is interesting is that in November 17 2015 in v0.3.6 there was a secret open source release of Mist (https://github.com/ethereum/mist/releases/tag/0.3.6) that essentially served as an early access programme.