Strong, static typing has additional benefits, especially when it comes to optimizations. The more restrictive semantics allow the optimizers within compilers and interpreters to make assumptions and decisions that could not otherwise be made. This in turn often allows for greater optimization techniques to be applied to the code, improving runtime performance and decreasing code size.
Haskell has even more going for it. Another major benefit is the availability of several interactive environments and interpreters. GHCi, for instance, is actively maintained, and is of a very high quality. There is also Hugs 98, which is a rather complete implementation of Haskell 98.