One of the things that I like about the idea of building a DSL is the idea of users being able to express, in fairly user-friendly terms, the actions they want to take. For example, Daniel Spiewak has a great example of a DSL built in Scala using Scala's parser combinators, and the resulting text, while certainly not English, is a very readable form. But in of itself, it seems it's been a hard sell to the general community, who look at GUIs as a far more intuitive way of doing things. (Note: I disagree with this; I don't think GUIs are more intuitive, I think GUIs are more self-explanatory, once you've learned a few basic principles, like moving the mouse, clicking the button, and recognizing which elements are clickable and which aren't.)
I think I've finally figured out where an English- (or other human spoken language) driven DSL can be far more powerful and intuitive than a GUI.
Voice. Or, specifically the world of telecommunication devices as a user interface device. Not as "putting-a-GUI-on-a-phone"; I think this is a red herring and ultimately unproductive line of research, iPhones notwithstanding. I mean, literally, talking to the computer.
Imagine a field repair agent, coming off of a repair call, calling back to the office to say the repair was done: "Ticket number 451123, status complete, note Mrs Johnson really needs to stop washing her clothes in the dishwasher." Hanging up, he moves on to the next ticket in the list.
Meanwhile, on the other end, voice-analysis software has done the basic job of transforming words into a line of text, which is fed to the DSL for processing.
Or, the field agent texts the message to a company account, which again passes it directly to the DSL for further processing.
I am firmly convinced that this style of user interface--one we use every day--is the way that mobile devices should interact with enterprise systems. Forget trying to do complex GUIs on a device, forget even trying to simplify down the complex GUI into a simple GUI--just use your voice and a well-understood shared protocol (the DSL itself).
It's the ultimate thin client.