Order flow is a very useful tool for vendors to take money out of the pockets of those who have still not learnt that order flow is useless.
I believe time and sales side is pretty useless. However the Dome is another story and not useless at all, and took me like 5th year of watching it to figure it out very useful patterns, but it is not like on a chart and as danielc1 posted of "4 you can 'see' four different scenario's" is the problem of traders of trying to "see" and be able to use. What I discovered, vendors do not make what I found as they never found it. And if too many had it, it would end.
As far as what you can see, if I am wanting to put a sell limit ie. 2680.00 and I see bid volume at two thirds less than ask volume and it building on ask side up 3 levels, I will cancel my sell limit and can always hit the bid side if wrong, but at least twice a day scalping wise I will cancel the signal cause market changed trend or if trend not change, I can get in at few ticks higher. But I am not trying to trade both side as am very system oriented with defined signals. Few times an hour you will notice inverse volume on the Dome where four levels has more volume than nearby and often this is a magnet, so again I will either pull my orders and wait or if in trade, pull limits to exit and make more ticks.
What I find much more interesting lately is how huge traders and HFTs can push the market a few ticks, like almost all doing the same thing together at same time, their entire aim is to take advantage of weak financial traders I believe, but it has actually been going on for decades, humans have great fear of losing, so fears are challenged much more than most think of when markets waffling around previous pivots only to return and go beyond highest low little bit in downtrend. So say there a trend line and traders jumping onboard of breakout, it goes down a bit, and they move stop to breakeven or risk couple ticks and on next bar BAMM, orders filled at breakeven or losses, this where I see order flow get heavier and I will jump onboard to sell. Happens several times a day, can make pretty good living just waiting for this to happen, but one does have to have good chart reading skills on knowing when you in a trade and it not working out and then market is going your way to give you an opportunity to get out and not look for big gains. You not only have to be disciplined on waiting for your signals but be able to get out cause you reading the price action to just take a tick or too much time has passed and get out at entry price. Really good signals allow one to get in and price never comes back.