Hey Dominic,
composer doesn't require PHP 5.3 namespaces.
foo_blah works just as nice. I'm using both "at work".
Anyhow — I made good progress over the weekend. Hoping to publish something by Wednesday.
One thing im wondering about composer/packagist. Is there an API through which RC or a plugin can offer a plugin admin page inside roundcube. If not, I think that is a serious negative.
Cor