That's true, I shouldn't mix up the two - the real complaint is about the tooling, but it's in refactoring tasks that I really feel it. For example, say I want to rename a class: If I'm in java/eclipse I can command-option-R, type the name, and press enter. Total time about 2 seconds. If I'm in sproutcore I have to search/replace the whole project searching for references which takes minutes and is tedious.

The reason it is difficult is because you can't use any of js tools that leverage a js interpreter - your code isn't valid until it's run through the sproutcore build system (which, as previously mentioned, is pretty slow).

That is pretty much standard in dynamic languages, including Ruby and Python. It's what I miss most about strongly typed languages, like Java and Scala.