From the Scala discussion list...
I bet 90% of the type system goes over my head.Me too. I think I gave Scala a fair shake for a few days. I have programmed a fair bit more than that in Haskell seven years ago.
I "get" functional programming when it comes to lists, recursion, higher-order functions, lazy evaluation, even monads at the "pragmatic" level of state, I/O, etc. in Haskell.
What I don't "get" is thinking in the various type systems. Maybe this could be called "type-first programming" as opposed to "test-first programming".
For this reason I believe, and the discussion thread, with the few posts it has, starts to confirm, that Scala has a tough row to hoe to become significantly more popular. A book is in the works, and perhaps the momentum Scala has gained so far will promote more in the "how to think in Scala" category.
As it stands I am ready to put Scala alongside Haskell, on my shelf for programming languages: interesting, not my cup of tea, nothing I will invest in at this point, but I am willing to be convinced if others do the leg work that makes the case for taking it back off the shelf.
I remain a dynamic language fanatic, especially a test-driven one, where small, incrementally developed tests are my program's hypotheses, as opposed to various type systems.
I would like to see other languages follow Scala's lead in finding fairly simple ways to become significantly more concurrent within a JVM. Either that or abandon the thing for a better platform.