I was introduced to Quicksilver last year by someone at the Rails user group. I’m not sure how I survived on the Mac without it. I used it for launching apps, appending to files, and jotting quick notes that went straight to kGTD. Incredible productivity booster.
And I just quit using it, and bought LaunchBar. Why? Stability. QS is great, but it crashes frequently - sometimes 5 or 6 times a day. For no apparent reason. Yes, I know its beta. Yes, I know its free. Yes,yes,yes. LaunchBar is more limited, yes, but it is rock solid. And fast. Seemingly faster than QS (although I have not measured it in any way…). If I can find a script that lets me access kGTD from LaunchBar, it may be a permanent replacement. (The only one I’ve found so far seemed to have a problem on the download page)
UPDATE: ..not that anybody but me really cares... :-)
Going to stick with LaunchBar. No crashes, fast, and the advanced kgtd script works with the new version of LaunchBar as easily as it did with quicksilver.