Early in the interview it asked if I purchased a Hybrid or Electric vehicle. Later it asks for year/model date of purchase and date put in service. $2600 (for me) ends up on line 55 of the 1040. I am using TurboTax 2006 Deluxe for Federal and State.
Hmmmmm.
I opted to let it do it's own updates without prompting FWIW.

Update: I did a little googling and it seems TurboTax will let you e-File but warns you you have a Non-Final form if you paper file. Hmmm? I guess the $14.95 gets you a better chance of being audited? At any rate my e-File shows "Accepted" for both Federal and State with the Alternate Fuel Credit included. Go figure.

ymmv