I've only been tinkering with GM mode for a little while, but It's missing some basic functionality for containers that I figured was a no brainer. For example, instead of being able to directly place items from the Creatures/Items panel into a container, you have to drag them into the world, and then drag them into the container. You're also unable to re-roll the randomly generated contents of a container; for example, if you want some random loot in a chest, but you don't like what the chest has when you first put it down, you have to delete it and place another chest to get a new random sampling of goodies. Not a huge deal (I mean, you can always just place whatever you want in there), but it's a little inconvenient at times.
