What is the point of a dock on a MBP. My cinema display has DVI firewire and USB. Three cables which are a lot faster to hook up than some clunky 1990s docking device. The point of a laptop is portability, if you want a stationary point buy a desktop.
BTW there are companies that make docking devices, I believe Bookendz is one of them.
The point is simple, you don't have to plug anything in. Drop and go. Sure it is simple to plug cables in, but tedious. Having a port replicator doesn't make it a stationary computer by no means. I requested it at my previous job and I requested it at my current job because I have to take my computer home every night. My thinkpad at the moment handles this very slick. It also makes the desk look clean when you remove the computer since there aren't unplugged cables laying everywhere.
I would love Apple to come up with a better solution than using some other companies 2nd rate, piece-meal approach. Like I said, IBM (Dells, etc) have a much better solution than Apple at the moment.