Samsung began rolling out Jelly Bean for the Galaxy S II back in February. The good news as of today, that update is now available for those with T-Mobile. The carrier has detailed the update process and two things stand out as needing to be known -- the update is large and it is not available over-the-air.
Details coming from T-Mobile note the update as being available only by way of Samsung Kies. The update measures in at 756MB in size, which probably speaks to the reason why the update is not available over-the-air. That speculation aside, the update will bring your Galaxy S II up to Android 4.1.2 and have it sitting with baseband version T989UVMC6.
Also, as the update is noted specifically as being "Kies only" we are not expecting an over-the-air option to arrive. That said, those with a Galaxy S II with T-Mobile can now update to the latest release. The carrier didn't offer a specific changelog for the update, however given we are seeing a jump from Ice Cream Sandwich to Jelly Bean -- we know there are certain items you can look forward to seeing as a result.
One of those goodies includes Google Now. You will also get the improved notifications which means more information and more options directly from the drop-down notification shade. By this, you will now be able to see the full text of a text message or the full image from an MMS message as well as the recently added ability to reply and archive a Gmail message. Finally, this update will also bring the smoothness that comes along with Project Butter.