First, you must be business owner or use it for work (commuting does NOT count).
You can write off the sales tax if your not using for business, but, if your state income tax withholding is more than the sales tax you won't get any benefit.
Second, the laws DID change recently. Used to be you could write off 100% in the first year. Now it's limited to 25K the first year and you depreciate the balance over time.
Heres more info -
http://www.irs.gov/businesses/small/...137022,00.html