Release v2.0.0
The update from v1.x to v2.x is a breaking change -- the v1.x used the XmlSerializer for reading from the API and writing out cached copys of it to file. This is generally okay, but the XmlSerializer is not as fast as the DataContractSerializer. The DataContractSerializer is much faster with large data sets, but loses its NHTSA API compatibility.
To strike a balance, the XmlSerializer is now mainly used when reading from the NHTSA's API. For serializing the data to disk, I would recommend using the DataContractSerializer methods.