A second generation implementation has since been developed using completely new browsers that take fuller advantage of the type system. Strongtalk has been used to write several large libraries, including a complete blue book base library implementation. The implementation has the highly desirable property that it imposes no overhead unless the typechecker is actually invoked. When the typechecker is used, memory overhead is small, and incremental response is good. Experience using Strongtalk has supported most of the assumptions of the original type system design.
Type annotation enhances readability of code.
Typechecking can actually ease the development process. It detects many bugs that otherwise show up during debugging, but faster. Also, the type system occasionally detects problems that lurk in working code for extended periods of time. The most important change introduced into Strongtalk is the move from structural to declaration based subtyping. Error messages produced by structural checking are poorly localized and very hard to understand.