For those upgrading from 1.x to 2.0 or newer, please FIRST upgrade your media module 1.x to the latest 1.6 release, then once you have done that THEN upgrade to 2.0.
note, these instructions are out of date and refer to a pre release version of media 2.0, the upgrade path should be much smoother with the latest 2.0 release
I noticed a few places where people are requesting instructions for upgrade from Media 1 to Media 2. I did this today and I've written up some short documentation (below). Please let me know if there is a better place for me to save this documentation for others to see.
I successfully upgraded to Media 2.0-alpha2 on an enterprise level site. This is somewhat tricky to execute, since there it requires an update of File Entity, too. File entity must be upgraded first. Then, a cron job is required to allow File Entity to classify the site's existing files into its file types (image, video, etc). Then, we can proceed to enable media and related modules. Here is a step-by-step outline of what I did to accomplish this cleanly. I also cleared caches between many of the steps below (for example, after enabling a module). 1- Disable media and file entity modules (this will disable brightcove_media, media_internet, and so on).
2- Uninstall media and file entity modules.
3- Remove, download, and enable the newest version of File Entity (2.0-alpha2).
4- Run cron via drush elysia-cron.
5- Remove, download, and enable Media 2.0-alpha2.
6- Enable each sub-module of Media one by one.
7- There were no updates listed when I ran drush updb. What's important is enabling the File Entity module first, running cron, then moving onto the Media module. Otherwise, drush started throwing missing DB table errors and my site crashed.
*** EDIT ***
For simpler upgrades, see comment 21 by @ChaseOnTheWeb