There: https://github.com/godbout/AlfredKat
Get your KAT torrents without all the advertising crap. Type "kat" followed by what you're looking for, wait a bit (it's quick), choose your torrent and make some space on your HD.
Now you can also use #tags.
There's a KAT workflow already on packal.org, but it doesn't work for me (SSL error). I contacted the author but got no answer, so I built this one. If the other one on Packal works it might be better to use it, it might have more options, or maybe not, I don't know, la la la la la.
NO SETUP! But the KAT URL is an Alfred workflow variable so you can replace it with a mirror in case the main site is down.
The workflow opens the magnet with the magnet default application of your Mac. If you prefer using a command-line client, you can add a cli variable in the Workflow Environment Variables. The value should be the full path to your torrent client with a {magnet} variable that will be replaced by the selected magnet (e.g. /usr/local/bin/transmission-remote -a {magnet}).
You can also copy the magnet to the clipboard rather than opening it (and starting the download) by using the ⌘ modifier.