Just did it on April 10. If you have rooted T-Mobile Samsung Galaxy S2 T989 phone with version 4.03 Ice Cream Sandwich do not waste time trying to use Samsung Kies for this Android 4.1.2 Jelly Bean OTA Update. Use this excellent guide to accomplish this task with ODIN.
Please note that instead of recommended ODIN ver. 3.04 in this guide I have used version 3.07 which can be downloaded from here: