Wishbone: Well, I'd say it has all of those things to begin with. Unfortunately, a while into the singleplayer campaign, the difficulty very suddenly (from one mission to the next) ramps up
considerably, which led me to quit the game back then, which was a pity because I was really enjoying it up to that point.
That's quite the same thing in my experience. I stumbled on a time critical mission that I *almost* beat 3 times in a row, but it made took a break from the game and I never went back.
For those hesitating : it's really a great game, the base building is quite unique, the base "eating" is unique and awesome ... it's a great experience (it's far from perfect but the originality in the design is worth the time and money). I really hope the expansion will make its way here, it would be a good reason to restart the whole thing.