Recently Mac developers have been reporting that it's taking a really long time for Apple to review their submissions to the Mac App Store. In fact, the Average App Store Review Times website says that reviews have been averaging 26 days. By comparison, the average iOS app is reviewed in about a week. And while iOS review times have been getting shorter, Mac app review times have been getting longer.
For a while the slowdown was believed to be related to the launch of iOS 6, which might have caused Apple to assign more reviewers to iOS than Mac apps for a while. However, no one is sure why the delays are continuing, and Apple hasn't commented.