One of the primary complaints about JSF is speed. We have paid a lot
of attention to optimizing server-side state over the past few years,
but we can also optimize the processing on the client. When a
component is updated via Ajax, currently we render the entire
component, even if only one property has changed. It would be much
more efficient if we sent only the changed properties via JSON and let
the client-side representation of the component update itself
accordingly. I have implemented a limited version of this for one of
my clients, and Ajax updates are noticeably faster. Updating the spec
to support this would not be a major change (because components would
opt-in to this feature), but it would have a dramatic affect on
client-side Ajax updates.
I will post a more formal proposal later.