One item you strive to avoid when you design and implement a feature is unexpected behavior.  Unfortunately there is one case we couldn't avoid with Lambda's in VB9.  I just ran into the this problem when coding up a handler.  I wanted to disable a button when the text of particular TextBox was empty.  I wrote the following code to handle the situation.

AddHandler c.TextChanged, Function() okButton.Enabled = (0 <> c.Text.Length)

This doesn't quite do what I intended.  This instead will simply compare the two values. 

In VB9 Lambda Expressions are always an expression.  In version 9 of VB, there is no concept of an assignment as an expression.  There is only a statement version.  As a result this doesn't do anything useful. 

This has tripped up a few people along the way.  It's an unfortunate side effect of only supporting expression lambdas. 

I was able to work around this by defining a function which did what I intended.  I called this function in the lambda expression and the problem was solved.