Update 3.10 adds features like voice message support and a calendar application, as well as an overall increase in the number of apps you can have on your home screen, bumping the limit from 100 up to 500. The aforementioned calendar app can be synced with your Google calendar, which is no doubt a handy feature as well.
The system's Content Manager app is also getting a "Manage Content on Memory Card" option that allows to you better manage all of the content stored on your device's memory card. A very useful feature, and one that I would have expected to have already been available by now.
For the full rundown on everything in this new update, check out Sony's extensive list of changes right here.