All of the above for sure, but my first question would be warranties on all of the components, including also the labor and installation. The batteries warantee will be an important one. I would ask if the inverter will be a large one unit piece, or will they use individual micro inverters on each panel, and have them tell you why they prefer their choice. If you are wanting battery feed back when the power goes out, ask about the installation process as to how the are planning to wire the unit to prevent feedback into the grid. I've heard of some power companies not liking this kind of system due to possible feedback to the grid while a repair is being done to the downed grid at the same time. Also check into the efficiency and consumer reports of all the package components involved.
They will most likely want to mount stationary roof mounted racks to save them time, but do ask about a pole mounted sun tracking system, and when they tell you you don't need that, ask them to prove why not. Also ask about lightening protection.
How old is your roof? Do you have a well ventilated area for the battery bank, and approximately how far is that area from the fuse box?