They definitely aren't pioneers at this. Steam (a game store) has been doing this for over 5 years, and started offering Mac games as well about 8 months ago.
That's fine for Apple software, but you can bet that 3rd parties aren't going to be chomping at the bit to give Apple an extra cut of their profits just to prop up this new app store. It may be a boon for indie devs, but that hardly means it's going to revolutionize anything. Microsoft and Adobe are both absent at this time, so no Office or Photoshop. I'm sure there are plenty of other examples, but you get the point.
For expensive programs like office and photoshop I wouldn't expect much interest. For anything that sells for less than ~$20, I'd expect huge interest.