>> blocks are much harder to debug. They're basically useless black boxes in
>> inspectors or debuggers, whereas receiver+selector can be easily examined,
>> changed, etc. Late binding wins, again ...

> I understand that that's the case at present.  But ideally, can't the tools
> be improved to be more useful with blocks (e.g. show the decompiled
> version), given that they are a useful part of the system.  It seems
> backward to me to not use something powerful because the tools are weak.

Did you have a look to LambdaMessageSend ? Basically it's an AST in the 
form of nested message sends wrapping a block which is its compiled 
form. So it has the speed of a block and the apparent structure and ease 
of manipulation of a MessageSend.

Stef