Everything I see pertaining to Blend for Visual Studio 2012 talks about making Window's store apps. Am I correct in assuming it can be used for regular desktop applications too?
At the moment Blend for Visual Studio does not have support for building WPF or Silverlight applications enabled. But, it will with the next update. From that point on you will be able to design regular desktop apps using Blend again. Until than you could use Expression Blend 4 which is available to you if you have an MSDN subscription.
You can read more about the upcoming update for Visual studio here and download a preview.
There's an earlier preview of Blend available that supports WPF too. You can read more about this on the BlendInsiders blog. The only drawback with this preview is that it doesn't have a go-live license yet. It runs side by side with Blend for Visual Studio.
Although it should be possible to build an application entirely in Blend, I would recommend writing your code in Visual Studio and only work with you XAML in Blend.
Update: With the release of Visual Studio 2012 update 2, support for WPF is added to Blend. More about that can be found over here.