It seems that the advanced email preferences are not well featured in the Subscription page.
I think being able to subscribe to just the first message in a thread and then follow any of interest is a very powerful and appealing concept. In fact, I have changed that to the default preference for one group I own.
Right now this option is BELOW signature on the subscription page and is additionally hidden, only visible when the user clicks on Advanced Preferences. I suggest at the very least it is promoted to the space above signature.
And I think that somehow it needs to be featured, either by a better label or layout.