I watch market depth a lot and find it to be very valuable. At first, I had no idea what I was looking at and used it completely wrong, but after some time I have grown very fond of it.
One of the great things is to suddenly see a lot of bids or asks getting pull away several layers deep. If this happens a lot, then you know that as soon as the price moves against it, its going to clear a lot easier.
Also, you can watch the number of contracts sitting at the immediate bid and ask. If the bid or ask drops away without the last price reflecting this, you know that its just someone pulling out. However, if you see this "pulling out" several tick depths, this could be a signal of a lot of traders / computers making new decisions.
Remember, the best information you can get about the here and now is in the here and now. I would never use market depth to trade off directly, but I did use it today for my best profit day ever -- I saw people pulling out bids when NQ was sitting near the HOD for the second time of the day and then I saw the bid getting hit relentlessly without any strong support in bid depth several ticks down.
That is when I made my best short trade ever.