Since I went from BASIC to Pascal in the late 70's, I've been fascinated by advances in computer programming languages. I don't get to follow them as closely as I would like, but I do like to see where the wind is blowing. One way I do that is by reading the Lambda The Ultimate site, which is a kind of multi-author blog with discussion forum focused on programming languages. From there, I learned about defmacro.org, which also has articles about programming languages. Although they are few in number, they are high in quality.
The latest article describes his adventures in trying to use the Haskell language to write a prototype. This is a great way to try out a new language, especially if it promises large productivity benefits, because you can quickly try out an idea in the new language, and then when you've decided on a design, translate it into your implementation language, such as Java.
Before I comment on defmacro's experiences, I want to say something about Haskell. I've run across several Haskell advocates, but I haven't run across many Haskell applications. Haskell, OCaml, and Erlang are languages that are getting some attention these days because they enable functional programming, which has advantages for maintainability, unit testing, and concurrancy. I've never tried any of these languages, but I have tried Lisp and Scheme, which also encourage a functional style, but they allow violations of pure functional programming. My understanding is that these newer languages make it easier to write in a pure functional style.
One obstacle to the adoption of these new languages is the different mindset of functional programming. I believe it is at least as big a shift as is involved in going from procedural to object-oriented programming. Also, most functional programming advocates are in the academic world, and much of their writing is not very accessable to working-class programmers. Defmacro helped this situation with Functional Programming for the Rest of Us.
However, there is another obstacle to adoption, which defmacro details. He tries to do a little bit of GUI programming in Haskell, and is unable to find a language implementation that will work. I think this is because GUIs are a low priority in the academic world. If these languages are going to see greater adoption, they need to be able to do practical things like manipulate files, implement network protocols, create GUIs, and build web applications. Not all are necessary for success. For example, Ruby is lacking in the GUI area, but it has a very good web application framework.