I think the early cars probably did not have all the production-version features of the P85D, and as such Tesla was restricting their use. Once new P85Ds are available I suspect Tesla will allow test drives, just the same way they allowed tests with the P85D. It is VERY annoying to have a test ride rather than a test drive. I am also sure that test vehicles can have the "insane" acceleration locked by software, as well as max speed.