I think IB has potentially a great product , however the experience I have had really put me off. The liquidy providers are not always executing instantaneously and you never know what may happen , it's not IB per se. What IB should do first is changing the way stop s are executed which to me is a huge problem. I am surprised noone has mentioned that yet . ( see stop trigger method). To trade larger size I prefer Globex, the rules are the same for everyone, no tricks no "Ooh but that was fast market we could not execute your order, sir".