Last Friday at work, I installed Google Desktop and it's already come in handy several times. This article provides a good overview of the features. At first, I was a little reticent to install a program that is "watching" everything that I do, but the upside is that I can search for virtually anything anywhere and get consolidated results almost instantaneously. Search for "brooklyn +Howard" and I get the emails from Rob about the "Seasons of Praise" project. Search for "digital rebel" and I get the IM conversations that Lydia and I had, the web pages I've surfed to, and the emails I've sent with questions about the camera. The search results give a great picture (if not a bit wide reaching) of the search phrase without having to search for files... search for emails... etc. This article gives a great overview of how it works.
I'm still holding out for my copy of X1 to see how they contrast/compare.