Hi Will --

>
> The ninth issue of the LaTeX3 news has now been released in the usual
> location:
>
> http://www.latex-project.org/l3news/
>

This is very good to see.

Re space-skipping in xparse, I think tightening syntax to the point of
having a syntactic layer independent of command/environment vocabulary is a
good thing.  So, if asked, I would vote for only this:

\begin{pgfplot}[  plot options with or without newlines  ]

-- Bill

--
William F Hammond