This article is actually the one that directed me to the one that I posted yesterday, the one about Firefox Quick Searches. This is also by Gina Trapani of Lifehacker. It's a fantastic read and I highly recommend it. Make sure watch the movie in the middle! It illustrates everything very well.
The main reason that I love all of these command line, keyboard based utilities (in addition to the speed increase they provide) is because they are nods to the power users. They don't perpetuate the assumption that everyone needs the most simplified interface possible. Some people are willing to take a little pain during the learning curve to reach the goal of a having more power at their fingertips - not just simplicity at all costs.