There is a new breed of imaging apps that have come up, at the moment I'm thinking of Adobe Lightroom (mac only, currently beta) and Apple Aperture (mac only, v1.0 and could use some polish).  The good thing is they are rethinking the UI for the specific tasks at hand.

But the old stalwart in this space is Photoshop (currently in 9th revision a.k.a "CS2").  So why does the world need both?

I think it comes down to the UI paradigm. 

One of the strengths of Photoshop has always been that it presents the user with a toolbox.  There isn't a button to make embossed text for example, however useful it might be.  The UI design expects you to know how to combine selections, masks and blend modes to create an embossed look for you text. 

This is a benefit not a limitation because PS is a creative application - your text bares the look of your experience and technique and matches the rest of the image perfectly.  If you want you can then record an action to make your own embossed text button.  Next to this, a generic embossed text button would give very average results.

The downside however is it requires considerable understanding of all the tools at hand to get the best results.

Compare to that the UI, or more the user experience, of Lightroom and Aperture.  These are focused on the needs of specifically digital photographers using high-end cameras (even one of these or these!) and pro workflow.  Because the UI is so focused they are able to encapsulate things that use to be a dozen clicks in Photoshop & Adobe Bridge & Adobe Camer RAW into one slick UI.  This is also a good thing.

So to examine the general case what does this tell us about UI design and user experience that can be applied to the applications we write?  I think it just underscores the need to directly address the outcomes the user is working towards in the UI, rather than having the UI just as a way for the user to interact with your program logic.

So look at your apps and ask... which UI are you; the toolbox or task-focused?