Should I upgrade?

I recommend that you update.  JI6 adds several helpful features and improvements.  In particular it also usually provides a dramatic improvement in the unreliable GPS function that has plagued so many Galaxy S phones.  However, I have read about enough problems with Kies that I would not choose to do it that way.  My suggestion: call TMobile and tell them you want the JI6 update and see if they can immediately send it as an OTA (over the air) update.  Those of us who have been using the phone for a while typically just got a notification a month or so ago that it was available for download and it just takes 5 minutes to do it.  Maybe yours will show up automatically, but maybe they can make it happen faster if you ask them about it.

JI6 refers to the build number of an update put out for the Vibrant a while back but it was still Android 2.1 so is now outdated. If you were to use Kies to update the phone now it would install KA5 which is Android 2.2. If you are wanting to update you phone I would suggest looking onto flashing a custom rom as they tend to run better and faster than the stock software.

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