Accuracy of the original human DNA datasets sequenced by Human Genome Project?
The HGP developed the first "reference" human genome - a genome that other genomes could be compared to, and was actually a composite of multiple human genome sequences. 

The standard human reference genome is actually continually updated with major and minor revisions, a bit like software. The latest major version is called GRCh38, was released in 2013, and has since had a number of minor updates. 


  Are the datasets provided by HGP still accurate?


Yes, in a sense, but we certainly have better information now. One way to measure the quality of the assembly is that the initial release from the HGP had hundreds of thousands of gaps - sequences that could not be resolved (this often occurs because of repetitive sequences). The newest reference genome has less than 500 gaps.