The best thing I've found (until they get a "Posts Since Last Visit" button) is to set your options in each forum.
1. Open a Forum
2. Go to the bottom and click on "Options"
3. Click on the "Date Filter"
4. If you visit at least once each day, set the filter to "Newer than 1 Day". (Or which ever limit you want) This will only allow posts to be shown than have been posted in the past 24 hours. NOTE: Setting the filter to "New Since Last Visit" DOES NOT work...at least for me. It just messes things up more than they already are.
5. Click the "Remember!" button. If you don't, all settings will default back after you leave the forum.
You're done...with ONE forum. You have to do this in every forum you visit.
This is what I've done and it definitely limits the results in each forum. Until there's a larger fix, it's the best I can come up with.
Hope this helps...