This may be obvious to others but I found it a bit counter intuitive and thought I would post a note as much for my own reference as for others. Consider the following code:

This will return the correct value (22222), but I thought it was a bit odd that the dot that precedes the condition does not actually take you down into the node, allowing you to still directly access the property you're after. I think this is a very smart implementation because otherwise it would be very difficult and convoluted to select a value based on a sibling value. It would likely require something similar to, albeit more complicated than, the methodology recently discussed by Mike Chambers.

E4X definitely rocks the house.