I'm not the person who mentioned QS but I'm still using it too. For me it's mostly inertia: Alfred can probably do everything I use QS for, but QS still works just fine, so why bother? When something breaks the 10% or so of QS's capabilities that I actually use beyond fixing, then I'll switch.
("Probably": last I tried using Alfred a few years ago, I think there was something I relied on QS to do that Alfred couldn't. I can't remember what it was, maybe Alfred does it now - but again, why bother? QS still does everything I want it to do.)
Also QS's interface looks cooler than Alfred's to me. Aesthetics matter.
QS was seriously broken for a long time. I understand someone else finally picked it up and started fixing the bugs, but I don't know why anyone actually kept with QS during the long broken period.
Even back when QS was under active development by the original author, it was still pretty buggy. I actually had a separate keyboard shortcuts app running in the background with a single shortcut which would relaunch QS for those times when QS decided to crash.
I am curious what you relied on QS for that Alfred can't do. Everything I remember doing with QS is doable with Alfred.
The great thing about Quicksilver is the grammar - it's actually object, verb, indirect object. That lets you do things like <file>, <email to>, <person>.
Alfred didn't have that basic structure when I tried it. I'm sure it's quite powerful, probably more so than QS given the latter's long stagnation. But I never bothered to figure out how to use Alfred effectively because QS is so easy and works great. There were a couple of bugs that were annoying for a while, but they've been fixed.
Kakoune doesn't mention the "indirect object" part of the grammar, but apparently it'll prompt for more information when needed, so it's pretty close.
Alfred does use that structure, and as far as I remember, it always has. I can indeed do <file>, <email to>, <person> in Alfred (though my most common object, verb, indirect object sequence is <file>, <open in>, <app>).
("Probably": last I tried using Alfred a few years ago, I think there was something I relied on QS to do that Alfred couldn't. I can't remember what it was, maybe Alfred does it now - but again, why bother? QS still does everything I want it to do.)
Also QS's interface looks cooler than Alfred's to me. Aesthetics matter.