I’ve been a long time user (3+years) of Quick Silver as a task launcher and general tool for keeping hands on keyboard rather than a mouse.
Around 6 weeks ago I decided to trial Alfred, Quick Silver got uninstalled about an hour later. Alfred lets you launch applications, web search, find local docs, open recent files etc etc with amazing ease. If you own a Mac, go try the free version either from http://www.alfredapp.com/ or the Apple Store. Once you are hooked go spend a few pounds to get the PowerPack and support an independent developer who is doing a great job.