I don't know how long the tax in Havasu has been at 2% but I am working on finding out (I would think it would be recent otherwise I would not have done my other deliveries there). If I would have known this at the time it would have been easier (and cheaper) to take delivery in California.
It was this way when I took delivery of mine back in Jan '04.
It's not necessarily the sales tax savings, it is the savings by not having to pay luxury tax year after year.
For resale, it is also better to have it outside of California. That way, when a potential buyer tries to bring you down on your price, you just tell him you're already saving him some 8% since it's registered in AZ.