The latest platform release adds Ruby 2.1.0-preview1 to the list of included rubies. If you’re curious about its new features such as refinements, required keyword arguments and improved method caching, now’s your chance to test them in your app.
The default locale is now en_US.UTF-8, instead of C.UTF-8 which was causing trouble to some users.
Postgres is now at version 9.3, letting you take full advantage of the JSON datatype (available from 9.2).
MongoDB went up to 2.4.7, which enables things like text search and returning symbols from the aggregation framework. See 2.4 release notes.
Firefox has also been upgraded, please run bundle update selenium-webdriver if you haven’t recently.
As usual, this is filed in our platform changelog.