Please can anybody tell me about...

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How is possible that many people have R1FA016 FW and others R1FA014 FW ?

performances in 016 :

The major changes which have been noticed are improved audio quality and the noise has been reduced with increased bass which makes the audio quality very good. Another change is in the camera quality in which shooting at night has improved drastically with less noise in the pictures.

The onscreen keyboard was a problem with the Xperia X10 as entering text was irritating. The problem was that sometimes a single touch was not sufficient to select a letter, but now it is better.

how is it possible this sonyericsson ?

Well, SE has said that the .16 update is provider based, so you'll only get it if you 'need' it.