Several months ago I started using Google Apps email for all my email on screenflicker.com. As soon as I made that switch I stopped receiving comment notification emails from all of my WordPress installs (which were 3 at the time).
Recently I've updated the most used WP install to 2.6 and the problem is still there. Does anyone have Google Apps email working with WP? Before you ask, yes I have the settings set to send emails on new comments and comments waiting for approval.