First of all I would like to say that you cannot compare WinBITS to other public download-managers like GetRight. At the moment, WinBITS is just a GUI (Guided User Interface) for the BITS (Background Intelligent Transfer Service) which is included in Win2000/XP. Until now, WinBITS has not been as comfortable as other Download-Managers.

BITS was primarily designed by Microsoft® for auto-updates (e.g. Windows® Update). The advantage of BITS is that it uses free bandwidth for the downloads. Your connection won't be slowed down if BITS is downloading files in the background.
BITS is a so-called "service" which is running in the background any time your system is running. Even if you close WinBITS, your BITS-downloads will still be processed.

With WinBITS, you can use BITS for you own purposes, e.g. downloading large files from the internet.