iTrader, when used correctly, could be beneficial to the WJunction community. The system is a fairly simple one to use. Below is a quick tutorial on how to leave feedback.
Scenario 1 (you are the first one to leave feedback)
Go to the users profile. Select View Completed Feedbacks under Feedback Score
Next, select Submit Feedback
The rest is fairly simple. Select what part of the deal you were involved in. You may have been the seller, buyer or it was a trade. Next pick a rating, a short description of how the experience was and the thread URL to the deal.
Scenario 2 (you are responding to feedback)
So you just received a notification you have feedback
w00t! Let me see
Now just click the first option there (little yellow looking paper) under Options
Finish the same as explained earlier. Deal URL will already be added
Another tutorial by immu here.