I know this is an old thread, but somehow I missed it until Seth revived it.
When I first began trading, I purchased the Delta book (at $175 it was and still is the most expensive book I have ever bought). I did it for 3 reasons, 1) I knew of Wilder's more mainstream contributions to technical analysis, 2) a professor of mine was a successful trader and was (or at least claimed to be) an original Delta member, and 3) I still believed there was a Holy Grail that would bring me unlimited riches.
The book itself is very compelling, especially to a newcomer to trading. I was quickly engrossed in the charts showing how the counts would repeat over and over. As a result, I started paper trading several of the instruments that had the most explaination in the book, namely the S&P, bonds, and the British Pound.
The flaws of the system quickly show themselves when you trade it realtime. Just like with other "counting" methods like Elliot Wave, interpreting a correct count on the hard right edge is very difficult, at least it was for me. In hindsight, its actually very amazing how well the turns fit the count. But in realtime, I was wrong as often as I was right, especially with the whole "inversion" thing, which if there is a natural order to things is nature's way of saying "gottcha!". In the book, there is only a small section on actually trading the count, and in my opinion, there should have been more discussion about that. Also, if you want software that does the statistical analysis to help you confirm turning points or plot them ahead of time on a chart you have to pay extra, and I never did that.
The other problem was that the counts seemed to work much better on the longer term charts and I have always been a daytrader. There is some discussion of a very short term count (4 day cycle) and I tried to discover the missing pieces of it that are not in the book, but Wilder doesn't discuss everything about it, instead using it as a teaser to join the Delta Society to get all the details (more money of course).
Anyway the point of all that rambling is that while I think there could be people using it successfully, its not a system that defies the laws of trading and drops cash in your lap. Maybe it could be used as a bias for other methods of entry/exit with a lot of practice. There very well may be some universal order to the markets, but no one has a grasp on it, only small glimpses from time to time. Otherwise whoever had it would have all the money.