RSBuddy is great, and it is safe. If you are really worried, or just being cautious (like I am), just don't give the client your username and password. It sucks if your bot gets logged out because you will have to be there to log back in unfortunately, but atleast they don't have your password.
Many people with billions of RSGP trust the client with their username and password though and so I would think that its completely safe.