I was just on normal difficulty, and my god. At first I was thinking"Aw man this is gonna be boring reaching 1500 kills", After a bit though it was pretty fun, and when you finally get over run it looks, and feels epic knowing how large scale of a battle it is
Fucking epic. I'm doing everything on brutal which definitely adds to the experience. Don't want to spoil anything so...once you get access to the Protoss part I suggest finishing all of it and putting Terran to the side for now.