> Some years ago, apparently Guido Van Rossum though 200 lines
I think it's better to measure the number of separate code entities (classes and functions and modules in Python) and how many different use-cases (ways of calling functions and object constructors) each entity is expected to cover... After converting to LOC, I'd say ~500 would be the limit. After that, it's a constant fight with TypeErrors, NameErrors, and AttributeErrors - it's just that everyone is already used to this, while not many know of any alternatives. Also, there are substantial differences between languages - in some 10 lines are enough to start complaining, while in some others I've seen and worked with ~2k loc code and it was manageable.
> many powerful compiled languages have appeared thanks to PL research, that are almost as expressive as script languages.
Yes, but on the other hand, some powerful static type systems for dynamic languages also appeared, and some of them are close to Haskell in terms of expressivity. The particular example here would be Typed Racket, which has a state of the art type system which is built on top of untyped Racket. It supports incrementally moving your untyped code to the typed one (whether a module is statically or dynamically typed is decided when module is created; as you can define many (sub)modules in a single file, you can just create a typed submodule, re-export everything that's inside, and move your code there one procedure at a time). Also, it automatically adds contracts based on static types, so that they still provide some guarantees when a typed function is imported and used in untyped code. There are many interesting papers on this, and TypedRacked is really worth looking into, if you have nothing against Lisps.
> Compile time type checking does not contradict testing, like you made it sound somewhat in your message.
Damn! I actually wanted to argue exactly this: that both tools are useful and both can be used together to cover their respective weaknesses. :) Looks like I need to work harder on my writing skills...
> I'm sorry if all this sounds condescending. I am yet to decide whether I should allow myself to sound condescending as the only benefit of age :)
Well, it didn't sound condescending to me, so no prob :) But, if you'd like an advice on this: please don't try to be condescending on the basis of age alone! It's totally ok to sound condescending if you have knowledge, experience and skill to back it up... Well, at least in my book :)