up to 10 second delay.....i just checked GM, and it updates exactly every 10 seconds. for some reason TXN seemed to be less often. that said, the delay really won't affect you all that much.
it's not really a delay, as in delayed quotes. it's a scheduled refresh, every 10 seconds. the data is realtime, but you get it as a snapshot every 10 sec. and I agree, it won't affect you that much. if the market is fast, open book might be disturbing.. well if you try to hit the inside market. anyway, it does not always work to do so. The open book has nothing to do with it. open book is no level II, and it's not the idea anyway. it shows you not hidden limit orders, that's it, that's all. making a profit with it some calls an art form. I disagree, but I agree in the difficulty to describe how to do it.