As usual, the Sony PlayStation Vita 1.52 Firmware update is a mandatory install. According to Andriasang.com the PS Vita update is simply another small bug fix.
To quote: "A number of Vita owners are saying via Twitter and blogs and so-forth that the update fixes a version 1.51 bug where the 3G system would not recognize your SIM card."
So far I'm unaware of any visible changes in the system or settings, however, this article will be updated as a change log becomes available on Sony's official PS Vita Web site.
System software version 1.52 for PlayStation Vita Update:
From January 16, 2012, began to update the system software version 1.52.
To become available and some features of the PlayStation Network features, updates the system software of PS Vita (Update) is required. PS Vita also system software, by updating, adding and security can be enhanced many features. Please use the update to the latest version.
The main features in system software update version 1.52:
The software system has improved the operational stability.