Beside of lots of small improvements and bug fixes, the most important improvement since BETA 1 is the addition of an (optional) admin interface for entity types implemented with the entity CRUD API. Modules may make use of that to provide their UI on top of it, whereas the defaults can be easily customized.
Entity CRUD API changes since BETA 1:
#973116 Entity CRUD API: fixed throwing exceptions in case of errors during saving or deletion. API change: In case of errors, an exception is thrown instead of returning FALSE.
Entity CRUD: do not export the 'is_new' flag
#970338 Entity CRUD: fixed module name of the entity test module
#976348 make entity_forms() more efficient to prevent unnecessarily loading UI controllers
#976346 Entity CRUD API: fixed notices entity_has_status() + improved the API docs
#976360 Entity CRUD: document that the access callback is required for the admin UI
Entity CRUD API: some small doc improvements
Entity CRUD: implemented the recently introduced hooks entity_view and entity_view_alter
Entity CRUD: added hook_file_download_access() implementation for entities provided via the CRUD API.
#962026 Entity CRUD: patch by klausi: fix entity URI links in the UI
Entity CRUD: patch by klausi and me: add a FAPI validation handler to ease validation of machine names for exportables
Drupal 7 development branch. It should be reasonably stable but I make no promises that it won't crash your site into a lamp pole and then blame it on its older brother.