One of the harder nuts to crack was how to make the jump from the onreadystatechange method back into my object-oriented scope. I tackled it using the Function() constructor to hard-code the path to my node into each event handler. The root node rested in global-scope, and a recursive lookup function did the rest. This way, I was able to keep track of multiple XmlHttpRequests at once, but it never did feel like a pretty solution. I ended up with multiple (okay, two) hashtable objects in the global scope just to tie up all my event handlers.
I wonder if your book addresses the issues that come with firing multiple XmlHttpRequests at once, and with connecting what's essentially a Visual Basic control to an object-oriented world. Did I overlook something blindingly obvious?