I'm also considering to buy a WD MyBook. Over here in Europe, they offer 3 years warranty for it, that's way more that any of the LaCie drives. Furthermore, it seems to be one of the cheaper options. I don't like that whole 'book look' idea, though.
One of my friend owns one and is pretty pleased with it. It's very silent, even though you hear the vibration a little bit if its standing on the table (not if you put a book in between). But I guess that's the case for any hard drive.. I even hear the one in my Powerbook vibrating now and then..