I have actually had the opportunity to directly compare a Beosound 6 directly with an iPod Nano . . . and the Beosound 6 is definately a big improvement in sound quality when using the same files and the same headphones. It's battery life is also ridiculously long. But there's no digital out, and I'm not sure that what it does for uncompressed file types, if any. B&O probably feels that a portable is a portable, period. I happen to agree with them on this one.
As far as the user-interface goes . . . they're about the same . . . meaning that I don't really like either one. The B&O's display is a little more readable, and I like the fact that the volume control is separate from the selection buttons. But its little leatherette case is silly, and makes it harder to operate the buttons. The shiney finish gathers fingerprints like nobody's business, and . . . well . . . it says Samsung on the back. I at least respect that if Samsung is heavily responsible for the product, that they tell you so.
I own B&O's other MP3 player, the Beosound 2, and really like it. It uses a standard SD card for memory, has no display, is very, very simple, and sounds great. For a portable player, I like it this way . . . I just want to take a handful of music with me, not my entire collection. I can stick the SD card in my laptop, drag over some music, and then put the card in the player. It even tolerates if I use the same SD card for my camera, with a mix of pictures and music on it.
Oh and their headphones are really nice and available separately . . . and they're really generous with the 3-year warranty.