Rated 5 out of 5 stars
XPather is an excellent add-on to the DOM Inspector. Sure, you can manually navigate 20-nodes deep into a tree -- sometimes. XPather is a quick way to get exactly where I want to go. Plus, the interactive evaluator is a big time-saver. It's got a small footprint, and does what I need.
My only quibble is that the xpath expression is not available in the DOM Inspector when diving directly to the element; but navigating to the nearest node and back fixes this.