I find autostore to be a much cleaner solution than the adhoc system amazon uses. With the amazon system you need a lot more space and staff to fill those shelves. In addition you have to be careful not to load them top heavy.
What about maintenance on a column? You have to stop the whole system, unload & disassemble part of the grid just to run a new cable or check for humidity or whatever on your structural columns.
That's the only downside I see. It's a very simple concept solving a very real issue and their motto "stop airhousing start warehousing" real hits home!
as for maintenance I would think a few strategic extra rows could serve that purpose without losing too much efficiency.
most the picking I am used to has both voice and light based picking with high velocity parts duplicated to the front.
For maintenance, there is an extra area outside the grid where you can move the robot out of the grid to do some maintenance work on it without affecting the rest of the system.