The (ivars) and (ivar-accessor) operators now do nothing and should be removed. Instance variables are now implicitly created and stored using associated objects, so there is no overhead for their potential use. The (cmethod) and (imethod) operators are still available but with a deprecation warning in the log. They should be replaced by (+) and (-), which are more consistent with Objective-C usage. The (def) operator is gone. It was carried over from Ruby and in practice, the equivalent (function) is preferred.
The <, >, <=, and >= operators now all rely on the compare: method to perform the necessary tests. They also now accept an arbitrary number of arguments (at least one!). Each operator returns t (true) if its arguments are ordered appropriately and nil (false) if not. For example, (< 1 2 3) returns t, and (< 1 2 2) returns nil This allows us to write functions like this one which tests that its argument is a list of objects sorted in increasing order: (function increasing (mylist) (eval (cons '< mylist)))