I think the program is an awesome idea and I really salute you for the effort of making it. But. There are some things that would really need some changes for it to be accepted by the masses.
Look into the torrent client. Azuregos is a java client and a serious resource hog. With it Oneswarm actually uses more juice than your average game O_o. That's quite impressive, in a bad way.
Make it possible to either name the files in the progam as you upload them or create categories for friends that are browsing your uploaded stuff. Or atleast make multiple folders viewable. Cause at the moment it's a living ant farm trying to browse a friends stuff. I checked the system and made a file with multiple folders and files (which then only showed the files upon completion) and ran the same file in a regular torrent client. To my surprise my intented folder categorisation was intact there and worked exactly like expected. Nice and userfriendly. Why not make it the same in Oneswarm. The functions are obviously already there. Let oneswarm implement it.
The user interface resets to default everytime you start the program. I doubbt it's intended soooo. Possibly a bug for me. Still annoying though :).
Userfriendly help or an introduction video. Right now the program is quite frustrating until you have figured out how to operate it properly. A help feature or examples in a video would help a lot. Most people I have talked to try it but ditch the program because they don't have the patience to figure it out.
Right click dropdown menus. Faster, more intuitive. Both in the program and in windows explorer. So you can right click a folder or a pair of files and simply click add to oneswarm and get a pair of options. Public, private etc.
Let you decide where it should put the torrentfiles. Not just where you want the data.
Direct Connect and FTP's have some great interfaces. I understand it might be impossible to simulate that but if possible. It would be totally awesome.
Long post. And I know I can have a somewhat negative language when giving ideas and criticism. I'm sorry for that. It is not my intention to demoralize you. I have great hopes for the program, which is why I am writing this post. And wish you total success with it. I'm really happy you started making it :).