There're a few things missing from the comm UI that makes using it sometimes difficult. A few things that would help:
[General improvements] -Shift-click to add to selection. -Control groups from 1-10 (as opposed to the limited 1-5 presently). -Double-click to select all units of a type on-screen. Arkanti has clarified that ctrl+click allows this, however, it would be nice to add for the sake of intuitiveness. -Construct units from multiple structures when multiple structures are selected as energy/res allows. At present, when multiple structures are selected the build order is simply ignored. -Add an artificial lighting effect for areas that are not well-lit; a prime example is trying to place cysts in Central Drilling on Mineshaft when the power has been destroyed, a near impossible task to do with efficiency. Added as of B198. -Clarify fog of war. Make line of sight more intuitive; for example, ARCs do not seem to reveal nearby units or structures. An actual fog of war effect would be good as well. -Show infestation when an outer edge of it is visible, not when the cyst creating it is visible; this causes too much confusion when trying to place structures around infestation.
[Specific improvements] -Selection boxing a resource nozzle will select it along with any units, even when beneath an extractor/harvester. Prioritize units above structures and structures above map objects when selecting an area. -Smart-cast cyst placement - if there are multiple hives selected, use the one with the highest energy (and create only one!) -Draw a two-dimensional effect on the ground where cysts may and may not be placed. It's frustrating to deal with elevation and walls that the cyst ring does nothing to clarify.
I believe these features and fixes would improve the fluidity and ease of use when commanding as either team, though particularly as a marine. Any suggestions or revisions are welcome.