The highlight of the 2.53 update is that it will introduce full-screen support for Adobe Flash Player content in the system’s web browser, allowing far more functionality for the many websites built entirely in flash. It also allows more convenience in displaying streamed footage in full-screen, if you have a stomach for the quality.
Update 2.53 continues Sony's philosophy of making small, quick, and continual tweaks to its system, as opposed to Microsoft's model of storing a features and releasing them all in one burst.
The update is expected to be delivered to consoles today. Alternatively, the update can be downloaded, carried and uploaded (when available) by starting here.