I only looked into Animorphic ST for a couple of minutes so far, but by first impression was, this is how Smalltalk should look like. Besides the system system, I like the Self-like browers.
I found the type-system the most unnatural part about StrongTalk. It feels displaced and if you look at methods like "->" in Object you can see that there are some rather nasty complexities associated with it (not to mention readability issues).
In Smalltalk (without types) no tool can exactly know the type of an expression and code completion (with is IMHO the best productivity tool of a modern IDE) cannot offer a valid selection of applicable method names.
That has been said many times and yet, I disagree. To the best of my knowledge nobody has ever tried to build a simple type inference system which just goes along with you as you are writing code and tries to discover what the types might be. Name completion and other utilities can even be used to tell such a type inference system about what types of certain objects are and I still think that you should be able to trivially figure out the types for 90% of the system without explicit type annotations. For the remaining 10% you _might_ want to use type annotations but I would hope that some better syntax can be found than is currently in both StrongTalk and SmallScript.
Currently, I'm working with a very large (VisualAge Smalltalk project which was grown over the last five years or so - and most original developers left the company long ago - and it's awful difficult, I want Eclipse (and Java) back. Never thought, that I'd say that but if mediocre programmers hack quick fixes into a system for a couple of years, Smalltalk becomes a mess. This is probably true for other languages, too, but at least types would give you some kind of documentation.
But of course you do realize that *optional* types would hardly ever be used by mediocre programmers do you?! So that an implicit type system would (arguably) be more useful than an explicit one that isn't used.
Cheers, - Andreas