Having recently filed an incident report (near collision), and gone through the interview process I was very surprised with the errors in the preliminary report - the supposed tracks made no sense, particularly in relation to times and distances, and the relative positions and performance capabilities of each aircraft. I spoke to the pilot of the other aircraft after seeing the report and he also commented that the flight tracks didn't make any sense and some statements were attributed to him he didn't make. Some 'facts' in the preliminary report that were based on my testimony were just wrong - maybe I didn't communicate well enough.
Whilst the final report was a vast improvement over the original, there were still inconsistencies. If neither of the two pilots involved had formally responded to the preliminary report, the final report would have been a worthless. As a post note, both myself and the other pilot had pretty much worked out what had happened when we first discussed incident.
The process was interesting, and it has certainly got a lot of the local pilots and operators thinking.