The major change is that :init is now always performed before loading a
file, whether loading is deferred or not. This is a change from before,
where the semantics of :init varied between demand and defer. The new
usage is now entirely consistent.
Also, because :init and :config now mean "before" and "after", the
:pre-* and :post-* keywords are gone, as they should no longer be
necessary.
Lastly, an effort has been made to make your Emacs start even in the
presence of use-package configuration failures. So after this change,
be sure to check your *Messages* buffer. Most likely, you will have
several instances where you are using :init, but should be using :config
(this was the case for me in a number of places).
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