There seems to be a problem with speed limits. With no speed limit engaged I am uploading at 130Kbs (to a specific user), when I check the box, and create an upload limit to 25Kbs, the upload slows to 5-6Kbs.
Also, when unchecking, and checking the 'Limit Upload Speed to' check box, I notice that current downloads are aborted, or disrupted. All bandwidth seems to cease temporarily.
Public Build 5 - OSX - Snow Leopard