Firmware version 6.1.E.3.7 for Xperia ion has been recently certified and is now rolled out to all devices worldwide.
The folks at XDA Developers report the update is now available in Central Europe, but will soon be deployed in other regions as well.
Although Sony has yet to unveil the official changelog of this update, XDA forum Senior Member Jozinek claims the new firmware version brings the Google Chrome browser.
In addition, some of the applications on the Xperia ion have been updated. Some performance enhancements and bug fixes have been included in the update as well.
The new firmware version 6.1.E.3.7 for Sony Xperia Ion does not require unlocked bootloader, which means it can be installed via Flashtool.
For more details on how to download and install this update for Xperia ion, check out the original thread.