Well, it seems that there is still an issue with WordPress and the Subscribe2 plugin. In deactivating the WP Mail SMTP plugin my email notifications about new blog posts stopped being sent.
So here I am again, in a final test (I swear i’m not trying to drag this out), reactivating that plugin to see if email notifications are indeed sent, which IMHO determines unequivocally that the issue is a problem between WordPress (2.9.2 and 3.0) and the Subscribe2 plugin with regards to the way WP sends mail.
So if you are experiencing the same issue, go and grab the plugin http://wordpress.org/extend/plugins/wp-mail-smtp/ and install it. It should fix your issue, and get you back to what you want to do – Blog, instead of trying to find out why your subscribers aren’t being informed of your latest musings. Unless of course your blog is about computer problems and tech and blogging that is.