Just opened a forum thread and wasted about 30 seconds on annoying rubbish. Went to hit the thumbs down and noticed it had one already. Thumb status isn't shown on the page before opening the thread. Suggest just showing some thumbs indicator on the menu.
As the thumbs are often used as a knee-jerk reaction based on greater prejudices towards the poster I don't think it would add much value.
We already have the "Recommended Posts" section at the foot of the Forums list so probably best to focus on the positive rather than the negative thumbs.