When starting with opensuse 10, I got used to the provided KT version 1.1rc1, and was not satisfied due to instability, thus I switched to Azureus. That worked safer, but annoyingly slowly and not that comfortable integrated into my KDE. Therefore, after several weeks, I read up on KTorrent and installed version 1.2 . I enjoyed and started to leech. But already during the download I noticed that there wasn't any upload.
Now, I have started some other torrents and played a bit with the settings ("0" had seemed to be interpreted as 0, what it shouldn't), and now some of the new ones start shily being uploaded.
Interesting: I just added a torrent downloaded with Azureus, and at once it started to get uploaded though it had only a fifth of leechers.
Is there any possibility to get KT seed those torrents? (the red 0,00 of the share ratio doesn't even look very decorative...)

KT should seed without problems. Zero for upload limit actually means no limit so changing that shouldn't have any affect on upload speed (except if you put a limit offcourse ).

We made lots of changes since v1.2 and they will be included in the next release (soon), so maybe your problem gets solved then.

Until then, you could try experimenting with different torrents. Try some from a public tracker and you'll see how people can leech from KT at high speeds

You may also try SVN version if you like experimenting (it's pretty stable).