The English version has the summary and appendices, with the main report to be coming soon. It is available at this page: http://naiic.go.jp/en/report/
(The Japanese version with the main report is here: http://naiic.go.jp/report/)
I haven't been able to view any of the files since yesterday. Every time I try to download the PDF files from the site, my PC freezes up and Adobe Flash crashes.
Main points (from various media reports):
The Fukushima I Nuclear Power Plant accident was a "man-made disaster".
TEPCO and the government was continuously kicking the can down the road, delaying the implementation of costly countermeasures against earthquake and tsunami.
It cannot be denied that the earthquake may have caused the damage to the plant.
The Prime Minister's Office's interference in the early days of the accident exacerbated the confusion.
There was little basis for the no-entry zone that the government set.