Aaron, are you saying you want to see subscribed threads, and see only the new posts on them?
That sounds like a good idea.
At present, as xiaxuele mentioned, click “User CP” shows only new posts to subscribed threads. (which I didn’t know about actually). The “Edit Options” link will let you default to get email notification etc for new posts to subscribed threads.
Under “Quick Links”. Subscribed Threads item shows all threads you have “subscribed” to. Of those threads, ones with new posts are in bold.
The “New Posts” link shows new posts from all threads, starting with the last post you’ve read.
On threads, you’re replied to, you should be presented with a “subscribe” option automatically.
If you look under “Thread Tools”, the secondary menu strip on the right side, under the ads but above the thread, you can select “Subscribe to this Thread” on any interesting threads.