From my experience, values imported into TurboTax do match the values shown in ItsDeductible. However, the market values in ItsDeductible change over time, since the market values of anything change over time, and no one can know the market value of anything at any current or future time. This also goes for other things like stocks, bonds, and real estate -- there's a reason why mutual funds price themselves only once per day, and it's at the end of the day to reflect the trading which has already happened. So Intuit can determine the market value of your items only after the day you donated them.
Why it fluctuates so much after the end of the year, though, I don't know. I would think within a month or so after the donation date, the estimates would be set.
Oh, and it's easy to compare, if you download a copy of your donation summary during the year and keep it aside and then do the same later on and compare the two, which it sounds like is what the OP has done.
