Eventually a final report will come out. If you use the search engine at ntsb.gov you'll find a "factual" report and a "probably cause" report. But it usually takes over a year before that happens.
The level of detail can vary quite a bit. In this example they recovered the Garmin portable GPS and were able to get data out of it. They measured the distance between propeller strikes to estimate speeds.
http://www.ntsb.gov/ntsb/GenPDF.asp?id=DEN06FA111&rpt=fa
http://www.ntsb.gov/ntsb/GenPDF.asp?id=DEN06FA111&rpt=fi