There are upsides and downsides to having proprietary cables, we have had this debate before. The upsides being the ability to use your player on a doc or with accessories that require more than just a USB connection. But the two biggest problems are you need to carry an extra cable when traveling and docks and other accessories are not cross brand compatible.
This is all about to change. In a bid to alleviate consumer confusion and an open source accessory ecosystem Microsoft, Apple, SanDisk, Sony, and Samsung have teamed up on the what they have dubbed the “MediaWire” (previous code named “RX-1″). The standard has been set but they have yet to decide on manufacturing facilities for this new “super cable”, though I have been told it will likely be available near the end of Q2 of 2009. There are some photos of this cable below. Keep in mind that this is a prototype, but expect a more refined version of this “one size fits all” cable packaged with your next player.