Good thread. Just got my 5S dock delivered today.
I ordered it at the same time as the 5S last Friday morning thinking I might use it. Now I realize this May have been an "on the whim" purchase.
I had good success and use with old Windows Mobile phones that had slider holster type cases where it was literally a snap to take the case on and off.
The box is small, likely not much bigger than the dock. Size in this case is probably not a concern, but rather compatibility with Case + 5S. Since I haven't decided on a case yet, was thinking that the Apple case might be compatible. But now that does not appear to be the case.
Reviews at the Apple Store appear to validate that the 5S dock is a phone only deal.
Customer Reviews: iPhone 5s Dock - Apple Store (U.S.)