David Buck illustrates the richness of the Smalltalk libraries - and the comparitive paucity of the C# and Java ones. Throw the "final" wrench into the mix and you get productivity loss.

Suppose, though, that Smalltalk could know (maybe by type inference or by declarations) the types of the variables and it implemented a kind of Intellisense similar to that in Visual Studio. What you'd find is that the list of available methods is about 10 times larger than those in C#. This highlights the fact that the C# libraries are really quite sparse.

Read his whole post - the table he posted is quite revealing.