I had a lot of problems (network stopped working after a while, deluge would close itself unpredictably, etc) with 0.5.4.1 on my VMWare Ubuntu Feisty Fawn. Installed and uninstalled multiple times, using various methods (apt-get, debian package installer, etc). Finally gave up and downloaded the 0.5.2 version from www.getdeb.net website. Works like a charm now I use bridged mode, and using a wireless connection to boot. Goes up to around 150KB/s depending on the torrent.

I personally don't find much of a difference between ktorrent and deluge. Both are fast.