C# was, to me, the best available language in TopCoder competitions. Once I had more than a passing acquaintance with Python, Lisp, Ruby and Haskell, it was annoying to compete in it. I spent a bunch of time trying to imagine a way to write in a language of my choice using code generation. Eventually I just gave up, and stopped playing (though this was one of many contributing factors)
C# feels dreadfully underdesigned to me. Despite its massive flaws, I still love Java for how consistent it is, and for how well-thought out it is. For instance, generics in C# aren't getting covariance and contravariance until 4.0, which I consider to be a fatal flaw. "List<? extends String>" makes so much more sense than "List<out T> where T : string".
That said, I am sad that the BGGA closures proposal won't make the cut for Java 7. I hope that some IDEs and APIs support it anyway.
I tended to use fairly flat data structures in my own code, so the extra hassle with generics didn't often come up. I did, however, use delegates (closures!) all over the place. They're verbose, but I mapped the delegate definitions to a resharper macro and it only took two keystrokes. That helped while writing code. It still was a pain to read, though, and ultimately the macro language wasn't good enough to do what I wanted.
The thing I like about Fortress is that it's a grown and growable language, with almost all constructs first class and exposed. Just like Lisp. But it's coming from the complete opposite direction in terms of syntax. Lisp barely has any syntax. Fortress gives you the most powerful production parser in a programming language, plus extremely adaptable syntax (where spaces can be operators!) plus a wicked way to render code, plus the ability to make your programs platform portable, adaptable, and parallelizable. It can be looked at as a programming language, true. But it can also be fruitfully imagined as a powerful framework for building one's own programming language. This is what I like to do with it. :-)
