I've been a Quicksilver user for many years. In many ways, it is integral to my experience as a Mac user. It's the kind of program that becomes part of how you use your machine, so much so that when I come to another computer that is not equipped with QS, I often find myself at a loss, grumbling about how inefficient it is to use a mouse for everything.
Quicksilver worked really well through OS X.4 (Tiger), so when reports of bugs in the program began to appear after Apple released Leopard, I was very, very worried. But my fears were mostly unfounded. Though it was definitely buggier, Quicksilver still worked reasonably well on Leopard. It's a true testament to Quicksilver that so many users were willing to put up with more than a few bugs. That's how amazing Quicksilver was.
But the other day, after installing the most recent QS build--even before upgrading to Snow Leopard--the app went from finicky to downright ornery (to paraphrase a tweet by Merlin Mann). I could no longer use the "Create alias in..." command with the "Current selection" proxy action. And something about the new build would periodically prevent me from moving folders in the Finder until I had logged out and back in again. Not to mention even more crashes than usual and an apparent desire to use the computer's fans to get airborne on occasion. I have since downgraded to the previous version, but that old fear of what will happen after I upgrade to Snow Leopard is back.
So I've been giving Google's Quick Search Box a try. And though I sorely miss a few hot-key triggers, QSB does almost everything I want it to, works similarly enough to QS that the transition is fairly painless, and has the advantage of being actively developed by the same dude who developed QS. No one who has used any of Quicksilver's advanced features would call QSB anything but a pale imitation at this point, but it definitely has potential.
As much as it pains me to say it, I think it may soon be time to put poor old Quicksilver out to pasture. Don't worry, I'll come and visit as often as I can, my pockets filled with apples and sugar lumps. You've been a faithful steed, but this cowboy needs to move on.