I used Quicksilver for years and loved it. Until it got abandoned and started crashing incessantly. When Google’s Quick Search Box came out (written by the same developer as Quicksilver) I was thrilled and switched immediately. Until it, too, got abandoned and started crashing incessantly. When the community came together to keep QS around as an open-source project, I switched back. And kept using despite the fact that it crashed incessantly because it was at least being maintained and was getting marginally better as time went on.
And then I found Alfred. In 2.5 years of constant use, I can’t remember Alfred EVER crashing on me. It has all of the features that I loved and relied on in both QS and QSB, is much more polished, stable, and, after 2.5 years, development is still going strong. As of this writing, there are 810 ratings total, with 769 of those being 5 stars, and for good reason.
The most telling thing I can really say about Alfred is that, after using the app for 2.5 years, and basically forgetting about it because it’s just always there, always doing its job, I actually WENT OUT OF MY WAY to find it in the App Store and write this review. There are VERY FEW apps that can claim that.