Ummm, maybe you forgot to uncheck "Open using Rosetta" in the release build?
I was enthusiastically awaiting how fast my day job application would launch now that I've eliminated the slowest thing. The debug build launched fast, the release build launched fast under instrumentation, the release build launched really slow from the Finder. What?? Was about to go up to bed, when it occurred to me I had switched on Rosetta for something months ago, and might have just forgotten to turn it off. Yep. Application launches quickly now. Users might even notice when this gets to them in a couple months.
By the way, when you are using Apple's Core Foundation XML Parser, you really really want to use CFTreeGetFirstChild followed by a series of CFTreeGetNextSibling calls to traverse the elements. You really don't want to call CFTreeGetChildAtIndex on anything approaching a large XML document.