Hmm, well just read through the thread and it seems most of the posters are swing traders. For swing trading, level 2 is much less useful. For intraday trading, however, here's what I meant:
Chart setups provide a visual explanation of what is happening to price. However, trading simply off charts will not provide an edge to anyone. This is because anyone and everyone can notice chart patterns and trade off them - there is so special skill required to do so. In order to have the edge, you need to bring something unique to the game - a skill that takes time to develop, and most importantly, a lot of effort.
My skill that I am constantly developing is the reading off the level 2 screen, which shows all the bids and offers in the market of a particular stock. By reading the level 2 screen, I am able to add another dimension to my trading and most often, I can see what is about to happen to a stock before it actually happens. So, I can get into a trade several cents before all the chart traders jump on board.
For example, prior to a breakout, if I observe strong bid pressure, I will usually jump on board before the breakout and be able to get a healthy profit out of it. In this respect, the level 2 screen is my trigger and also keeps me out of many a false breakouts.
I won't be right all the time, but with momentum trading, if the stock doesn't do what I expect it to do, I can be out with a small loss.
Hope this explanation was clear enough.