Basically, the topic centered around whether or not to always return $self (for method chaining) or a value (for, say, an lvalue).
With Want, by Robin Houston (robin), you can distinguish based on calling context. So, for example, you can tell the difference between these:
$val = $obj->method;
Want can do much more than this (eg rvalue subs, etc), but I find the "want('OBJECT')" call to be the most useful.