Updated: May 31, 2008
I have been using KTorrent since the 1.0.2 version, and each new release brought in some nice feature or improvement. This article reviews KTorrent 2.2.6, which currently is the last stable release for KDE3. The BitTorrent protocol was has been around since 2001, and it is one of the most widely used protocols for file-sharing, and many open-source projects encourage the use of it. Usually when a new distribution releases a new version, there are thousands of persons using BitTorrent to download it and share it to others in turn.
KTorrent is what I call a complete client for the BitTorrent protocol, and some of the highlights are: the possibility to download only a certain file/directory included in a torrent, instead of the whole content; you can easily see the files, peers, chunks and trackers available to a torrent while downloading it; you can easily create a torrent file and start seeding it; plenty of plugins are available to it, which greatly expand its functionality. The preferences dialogue allows to configure any aspect of KTorrent, like folders where you want the downloaded torrents to be placed, or download/upload bandwidths.
Search default torrent sites or add custom ones
It includes by default several torrent sites to search from, and you can add many more following a simple procedure. Just get to the website hosting the torrent files and enter 'FOOBAR' into the search box, then add the URL from your browser to KTorrent. Next time you will use KTorrent to search that site, it will simply replace FOOBAR with your search query. The default torrent sites should be enough for the average user though, to include some of them here: isohunt.com, thepiratebay.org or mininova.org.
Plugins take KTorrent's functionality even further
KTorrent 2.2.6 comes with several plugins which prove very handy, like a plugin for importing partially downloaded torrents from other clients (useful if you decide to switch torrent clients but don't want to lose the downloads to date), a plugin for searching torrent sites (loaded by default), or the RSS Feeds one, to keep you up to date with any new torrents submitted recently on a certain website.
Queue manager and system tray
KTorrent also features a Queue Manager, allowing you to set different priorities for the torrents you are downloading. You can also set maximum upload/download rates, as well as start or stop all torrents. You can minimise it to system tray, and you can set the memory and CPU usage which KTorrent should use. It can also notify the user of finished downloads, with the possibility to turn the option off.
It's stable, I had no crashes with this version (2.2.6). Since the new KTorrent 3.1 is about to get released, this will probably be the last KDE 3.x version.
Create own torrent and start seeding
KTorrent makes it easy to create your own torrent and start seeding it, in just a few steps. This is one of the pluses it has over many other more simplistic clients.
Community and Development
I noticed KTorrent has regular releases, and now work is in progress for KTorrent 3.1, which will use Qt 4, at the moment of writing KTorrent 3.1 Beta 2 being available. The official website includes a forum, to discuss KTorrent or get help.
I love this client. Ever since I have been using it (over two years now), I could not find another one which fits better with my taste. KTorrent is also very fast and responsive, and it does not hang, even if there are more than 20 downloads at a specified time. The only minus it has is that it does not have any Handbook (or at least, it was not included in the repositories version for Debian), so the help is available via the forum.