OMG, they are fantastic ...
Today I finally got to go take a tour of an Amazon FC that is using the Kiva system already. This one has way bigger robots than the one I'll be in as they are a large item warehouse, but otherwise it's the same - just bigger robots and bigger shelving. It really is so, so neat. Our guide took us to a station and he input in the computer than he needed to do a "count" ... and the shelves started coming to him. Lined up. You could watch the little robots go under the shelving units when they were near - and then turn and lift and move the unit to the area - until several were in line for him. We got to watch them line up for stowers to stow to, and for pickers to pick from. It truly is so neat ... so awesome. And the warehouse is quieter, also. These guys make no noise.
If only I could have taken pictures!