I think the simplicity of WMM is great. I have Premier as well but when it comes to putting the movie together its a pain. Filters are nice though.
I think, if I were to do another movie in BL, I would probably add clips and sound in Premier and put together in WMM.
Sadly WMM lacks the ability to add multiple layers of sound at the same time. It also won't let you have empty space between clips.
