With the new plugin downloads system, it now makes a lot more sense to develop (or at least host) plugins on the wp-plugins.org SVN.
Having spent a month figuring out how it works, I've put together a short tutorial on using SVN on wp-plugins.org and setting up plugins for download through downloads.wordpress.org.
If you're interested, the article/tutorial is online here:
Developing with WP-Plugins SVN
Feedback, suggestions & corrections (as I'm sure there will be) always appreciated.
