I finally finished the campaign on hard difficulty and one of my biggest complaints is that you gain resources very slowly, especially in the early to mid game missions. I dont know if this is a problem with only the hard difficulty, but most of the time i was just staring at the screen waiting for resources so that I can actually continue the mission. The missions would be a lot more fun if you had something similar to escalation phases in the base building missions. I think another problem is that since there is no escalation to increase resource generation rate, upkeep tends to really impact how much resources you get.
Did anyone else feel that resources were a big bottleneck in the campaign. Besides that one issue I enjoyed the campaign.