Deluge
First of all I wish to thank Deluge's developers, because this torrent client is the best from the list of about 10 clients I've tried to use in Ubuntu. Of course it's not as excellent as uTorrent is for Windows platform, but as I can see, it's the best alternative (at least for me) for Ubuntu and, I think, for other linux systems. I also hope that future versions will provide more settings and features, so the client will be even better than uTorrent!
But as for now, unfortunately, I found some bugs while using this client for about two weeks (starting from version 1.0.4). Below is the list of them. I apologize if some of them were already discussed, but I just want to provide information about my own experience of using the client and problems I've found.
So, here is the list of bugs:
1. The most important: Deluge uses 100% of CPU. The reason is that it can't synchronously seed same file in two or more different torrents (as discussed here).
2. Problems when adding list of torrents from files:
2.1. Sometimes (I can't identify the exact reason) after selecting a torrent in the list of torrents opened from .torrent files ('Add torrents' dialog window) Deluge just crashes. I.e. all Deluge windows suddenly close and all deluge processes stop.
2.2. After adding a list of about 10 or 15 torrents and pressing Add button only few torrents will be really added. I don't know, why it is happening, but if I add all of theses torrents one by one, everything is fine.
3. Files, for which highest priority is set, are downloaded as if they have just 'High' or even 'Normal' priority. After torrent have been started, I marked two files I needed to be downloaded as fast as possible, as files with highest priority. In spite of these files really began downloading faster, some other files (with the same size) with normal priority were downloaded much earlier than these ones. There were many seeders, so the reason of faster download of other files is not the lack of people who have files that I needed.
4. When right-clicking the directory containing files to download (in multi-directory torrents) and choosing 'Do not download', nothing happens. However I expect that after these actions all files in that directory will be marked as 'Do not download'. The trick with context menu will work only after selecting the necessary directory, but if so, why this menu and options in it are available for non-selected directories then?
5. Seems not to be a bug, but at least a feature to be improved: checking files, that are already downloaded is too slow. As I can see, uTorrent checks the same amount of data at least 10x faster.
That all that I found for the current moment.
However in spite of all these bugs, Deluge is very promising project. So I wish a good luck for it's developers and I will impatiently wait for bug fixes and new cool features!
P.S. I use Ubuntu 8.10 and Deluge 1.0.5
P.P.S. Sorry for my English (as you probably guessed, it's not my native language
), but I will do my best to explain my problems and answer any questions, if needed.