The term 'beta test' has been somewhat diluted over the years, now often simply letting people play an essentially final version of a game a few days early to raise a little hype. DICE actually collected and is acting upon feedback from Battlefield 4's multiplayer beta, though, and a new blog post details improvements to performance, balance, and more coming thanks to the public testing.
If you've had poor performance on PC, DICE says in a blog post to "Rest assured that we're using the information we received to optimize the performance for the launch of the game." It's also ferreted out the source of abnormally high CPU usage on multi-core processors, and is working away on the bug which saw all platforms, but especially PC, stuck on the loading screen.
On consoles, it's making more controller options, and adding options to filter empty servers. The blog post also details loads of balance tweaks I shan't get into. They tweak balance.
DICE also actually used player feedback with the previous Battlefield game. How novel to use tests for testing!
Oh, and this elevator glitch is being fixed (I apologise for their mild cussin'):