Here are a couple of ways Turbo Tax could cost you money on your taxes:
1) When it imports tax data from Quicken, it ignores any estimated tax payments made in 2008. So if you made estimated tax payments around January 15, 2008 for tax year 2007, you need to enter them yourself on the Tax Payments Worksheet. Otherwise Turbo Tax will tell you to pay those amounts again. (If you go through the interview, you might notice that the January payments are missing. Or you might not.)2) If you received a state income tax refund in 2007 and paid federal Alternative Minimum Tax in 2006, then some or all of that refund should not be included in your income for 2007. But Turbo Tax won't tell you that. (It caught it as an incomplete form error in 2006, but I don't think it does in 2007 - correct me if I'm wrong.) This might not hurt if you're also well into AMT in 2007 because misreporting the refund as income will not change your total tax.
(Disclaimer: I don't know if the interview helps with these because I mostly skip it. I'm not an accountant. This advice could be worth what you paid for it. Any corrections will be cheerfully received.)