Civilization V, you're probably the strategizin' type. You likely called around, made comparisons (maybe even put together a spreadsheet -- we won't judge), and then chose the most strategically fortuituous preorder that you possibly could, finding the perfect balance of cost and value for your money.
But just like all of those late game German Panzers, Direct2Drive is throwing a last-minute wrench in the gears. Preorder Civ V via it, and you'll get immediate and free access to the classic Civ III, the last iteration in the series to stay 2D, largely viewed as one of the best versions of the game. Plus, D2D preorders also get the new game's first bit of Scenario Pack DLC for free.
That's a good deal. Of course, if you want to preorder the new Civ, you probably have the old Civ collecting dust somewhere on a shelf. But you might at least add this deal to your spreadsheet, just to see how it balances out.