I would be interested in the following feature, that you can find on a lot of forums already:
A way to get an overview of the topics that you have posted in, and that have new postings since your last visit. Preferably, you'd be able to jump directly to the first new posting in these topics from the overview.
I find such a search (which should be in the Forum Menu for direct access) extremely useful. It makes it very easy to keep track of topics you are interested in, without needing loads of email notifications. If such a feature were available, I would turn the "notify by email" off by default in my profile.
Discussion in: http://developer.qt.nokia.com/forums/viewthread/2948/