Nate,
This subscription option looks like a nice feature, but I'm afraid it has never worked for me. I've signed up for these notifications (multiple times) on multiple forums but have never received a message by email (including this one you just posted). Even if it did work, I'd still suggest a more traditional listserver (with a web interface/archive is nice!) because it gives you some idea of who you're reaching. With the forums you don't know who is signed up or if anyone will actually see your message. It's true that a listserver wouldn't allow you to pick only specific threads you're interested in monitoring, but I think the cost of viewing a few less relevant messages would be outweighed by the feeling that there's an interested community out there (and sometimes you learn things that you hadn't thought of). I realize a listserve may not be technically feasible with your setup (or administrative time constraints), but maybe there are tweaks that could move it in this direction.
In a possibly related issue, my computers never remember to log me in automatically, even though I've chosen that option multiple times.
Thanks for listening - Sean