As an amateur photographer and Photoshop “power user” for about half my life now, and wannabe interface/information designer, I’ve done a lot of thinking about Photoshop’s interface.
I love it, and I hate it. It’s by far the best tool around for the kinds of things I want to do to my pictures (I could write several pages about why the GIMP is inadequate). It’s an extremely deep program – the deepest I’m very familiar with – full of all kinds of little thoughtful touches that make it smooth to operate for experienced users. It has several very powerful abstractions for dealing with numerical manipulation of images, which when mixed and matched support a broad diversity of workflows and needs.
But – Adobe has been unwilling to ever remove anything from it, or change any existing feature very dramatically. With the result that it has accreted features and grown into a newbie-unfriendly mess, to some extent. Many of its features end up superfluous because there are better ways of accomplishing the same thing, and so they sit there in the menus and palettes crowding out the rest. The majority of the earliest tools should be radically redesigned to account for the more sophisticated interfaces (which is not to say more complex) and more computationally expensive algorithms possible on modern hardware. Many of these tools have literally barely changed in 15 years, even though users’ needs and hardware tools have changed dramatically: digital cameras have become ubiquitous and much better, etc.
I don’t have much use for Photoshop haters, but I’m deeply saddened that Adobe hasn’t faced much real innovative competition, and the whole image editor field has kind of stagnated as a result.