Jelly Bean Alpha ROM For Xperia T
Sony have already announced the new Xperia flagship, but still supports all the older mobile devices. Sony just released an Xperia T Jelly Bean Alpha ROM upgrade. The final Jelly Bean version for Xperia T will be launched by the end of March.
To install the new custom ROM you should have the Xperia T bootloader unlocked, which means that you will void your device warranty from Sony. Also unlocking the bootloader means that you will not get the official update when it becomes available.
The Jelly Bean Alpha ROM is focused almost exclusively to developers. It has only a limited set of features working. All connectivity is unavailiable (WiFi, Blueooth, NFC, FM etc.) and for example you cannot make phone calls or connect to the internet. Also the UI for the Jelly Bean has not yet been upgraded, and there are services such as Google Maps, Play Store, Gmail that are missing.
As you can understand this ROM is focused, as we said before, almost exclusively to developers who want to test their applications in the new version of Android of the Xperia T. Keep in mind that Sony has promised to upgrade Xperia T in late March and it appears to be in the right direction.