I will give a few of my thoughts:
The main difference between marathon and ultra, is that you will need to carry your own water on most ultras. Whether you use a camel back or a rig with two bottles, it had better be a good one. You should pay as much attention to the fit of a camel back as you would to a pair of running shoes.
If your ultra caries over into the hours of darkness, then your head torch becomes your visible universe. Make sure it is light, robust, and above all powerful. Make sure that you like the controls, which you may have to use instinctively.
All distance runners lubricate themselves, but in an ultra a problem can crop up somewhere you did not expect it. I carry one of those tiny tubs of petroleum gel lip balm, because they are light and can be used to perform emergency lubrications.
Duct tape can be used to repair any piece of kit, including the human foot. It is waterproof and strong, yet you can tear it with your bare fingers. The problem is finding a roll that is small and light.
I have had maps disintegrate in the rain. You can use a map case, but laminating them saves weight.
You must have protection against the elements if you roll your ankle in the middle of nowhere. Carry a survival blanket or most ultras. Preferably the silver one that absorbs heat from the sun even in cold weather.