I finished the human campaign. Got a couple of maps into the next race, but there seems to always be That One Map that frustrates and infuriates you, because while it's possible it requires HUGE amounts of optimization and not overestimating the kinds of forces you'll go up against, as you don't have the time to overbuild.
The human map one is all about setting up teleporters to get across the map and defend a building by the 20 minute mark. It's doable, key point: you don't need that many units. If you don't have a network set up by 12 minutes* and have started transporting guys by 15,* start over. You HAVE to cut it close, repeatedly. Doing that much isn't enough. Once you have the first wave, go back in time almost as far as you can, queue up some units, micro the future battle, go back to the present, teleport newly built units to the front lines. Repeat.
I was constantly using the same 3 minute window to do things I didn't have time for 3 minutes ago. I'd go back in time to build units, go to the future to micro a battle, then head back into the past again when my units got constructed, and transport them to the front lines (where they'd participate in the battle I spent time micro'ing). I was hopping all over the time line to save a unit, get the extra kill, or get units to the battle field. It was 20 "my minutes" of non-stop panic.
I'm at That Map in the second campaign, and haven't attempted it in months.
*Numbers kind of made up based on what I remember.