Hi Bill,
Thanks for mentioning my blog post. Before I say a few things about Market Delta, let me make clear that I am not affiliated with the firm, don't receive any commercial compensation from them, and my posts have not been solicited by them.
I first turned to Market Delta shortly after joining a proprietary trading firm in Chicago as their in-house trading coach. My concern at that time--and it has only grown since then--was that the data extracted from the DOM ladder was increasingly unreliable for decision-making among short-term traders. Bids and offers were entered and pulled from the book so frequently that it was difficult for most traders to obtain a true feel for nascent supply and demand.
Market Delta only tracks volume that actually trades, not orders in the DOM. It parcels transaction volume that occurs at the market bid vs market offer as a way of determining whether sellers or buyers are more aggressive at that moment. A useful feature of the program is that it can be set up with bars of varying lengths, so that you can see shifts in volume distribution over varying time frames.
I find Market Delta very helpful in trading the S&P eminis. It is not especially helpful in trading instruments that are very highly arbed, such as SPY. I know of professional traders who also find it helpful in the fixed income futures. Stock traders might want to track their favorite issues during a free trial to see if the program provides insight and a potential edge.
One other thing: a number of traders use Market Delta with Market Profile, the latter providing broader context for trades. This can be very helpful in visualizing breakout trades and failed breakouts that will revert to the value area.
This post provides a simple illustration of Market Delta; my blog has others, and I'm happy to answer questions. I'd also be interested in hearing from other traders who use MD, to see if their applications are different from my own.
http://traderfeed.blogspot.com/2007/02/how-to-identify-and-trade-breakout.html
Thanks again for this excellent forum--
Brett