Microsoft continues its marketing "battle" with Apple by launching a promotion at its stores in the US that lets iPad 2, iPad 3, and iPad 4 owners trade in their tablets for at least a $200 gift card. The devices have to be "gently used" and the offer is only available in Microsoft Stores in the US and Canada, according to Microsoft.

Previously, Microsoft had been recruiting Siri to bad-mouth the iPad, launched an iPad comparison site, and picked on the iPad mini, as the company ried to convince buyers for the great value of its Surface Pro and Surface RT tablets. However, the slow Surface sales had forced the company to cut the price of the Surface RT by 30 percent and nore recently, the Surface Pro by $100.

Microsoft is holding a special Surface event in New York City on September 23rd where it's expected to launch the Surface 2 and Surface Pro 2. Both devices include faster processors.

Microsoft's trade-in offer ends on October 27th.