Thought I would post the latest direct from Tesla. They have been working hard on getting some good solid answers to the whole tax and factory delivery issue and here is the response:
We have an update for all of our out-of-state customers who are interested in taking delivery at the Tesla Factory in Fremont, California. It is now clear per the California Board of Equalization Publication 34 & Regulation 1620 that all customers taking delivery in California must pay California sales tax. Non California residents who opt for delivery at the Fremont Factory must pay the local county sales tax (currently 8.75% in Alameda County). These taxes will be collected at the point of sale in California. The point of sale, by definition, will be at the time the customer (purchaser) takes possession of the vehicle. Customers travelling from states that have higher sales tax than the Alameda County tax may be required to pay the difference to their local government. We suggest customers contact county and local governments to verify their tax rates.
While these tax regulations will impact customers who plan to drive their new Model S back to their home state, we encourage customers to visit us and participate in the Tesla Factory Experience in Fremont. This program is designed for those who want to see the Model S production facility, tour the production floor, learn about the beginnings of Tesla.
Regardless of where you choose to take delivery of your Model S, we plan to provide a Tesla Personal Delivery. At your delivery location, we will provide an in depth vehicle overview and help you customize your Model S vehicle settings and personal preferences (Touchscreen, Homelink, Bluetooth devices, download music, etc). The cost of the Tesla Personal Delivery will be identical for those who opt to pick up their Model S at the Factory or have it delivered across country.