I thought myths 1 and 3 were well argued, but I couldn't find support for the claim that CEP isn't mature. Quite the opposite, actually. For example, Ivy cited AITE group's Adam Honore's opinion that CEP's use is expanding and cited a number of the public references like the FSA and Turquoise. I wrote an entry on this topic a few weeks ago as well based on initial visits with StreamBase customers and their usage. Public disclosure of initiatives like this argue for maturity, not immaturity.
Marc Adler from Citi said: "CEP is not this golden pill that you take and everything is solved." True, but this should be a safe statement about any kind of technology - you get out of it what you put into it, and especially in the sophisticated realm of capital markets software systems. Indeed, the longest pole in any CEP project is integration with the various OMS, EMS, middleware, and database components that often play a big role in any system. Pragmatic understanding of what it takes to deploy CEP, in my book, is a good thing, and Marc's comments are a helpful reminder of the best practice to apply sound engineering practice, especially when it comes to a relatively new technology like CEP.
I've spoken with Ivy numerous times over the year, and she has always written thoughtful articles, so I'd guess she would respect this rebuttal - frankly, I think the content of this article argues the opposite conclusion - that CEP is robust and maturing and reliable, not "immature."