I think it would be quite usefull to add an option that checks at program start up whether data on disk corresponds to the content of the XML file for each torrent task and ask the user what to do.
I often move from my portable hard drive files I have downloaded, without first removing the task from the task list. I know, I am lazy, but I believe it would be useful to have such an option.
For example, if BitComet starts and finds missind data from a torrent task already downloaded, then it pops up a window describing the torrent and asking the user whether to download it again or to remove the task.
From my experience, I recon that BitComet automatically reallocates space on disk and tries to download it again.
Also, it would be nice to have a splash screen at program start up that describes the functions that are happening rather than having a frozen program screen.
Again, congrats!