I’ve been using Mac OS X for a couple of years now and I just today learned about Quicksilver, thanks to an offhand comment in a friend’s blog.
Holy crap — Quicksilver is so incredibly scrumptious and I’m not even running it yet! Haven’t even downloaded it — I’ve only got 10.3 on my Mac mini and the Macbook Pro is on 10.4. Apparently, I can’t run the latest version of Quicksilver on 10.3, and I hate hate hate having to maintain two separate versions of software across multiple machines. (As an aside, this is one of my biggest pet peeves with the Mac world. It seems like every cool and useful application just drops support for previous versions of the OS, a year or two after the next release comes out.)