It does a couple of things neatly. In particular, it shows other species on their own parallel tracks of evolution at various stages. Even at the space faring level, you can see species trying to make it as a creature or tribe. The cell level gets left behind unfortunately -- you can't see any traces of it as you go from cell to land critter.
Another thing I appreciate is the existence of "epic" creatures. Giant godzilla like things that wander around and occasionally trash your troops. I managed to kill one at the creature level using cheats (so that I wouldn't have to go hunt for food at the same time), ranged poison attacks, and a bug where, for some reason, this one critter wouldn't follow me into a forest. I'd been firing and running up until then. Sadly, it didn't give me the achievement for destroying an epic creature at the creature level, but such is life.
They don't make a lot of sense, but they add a lot of color and strategic implications like "If I send my troops directly to that city, that epic critter is going to eat all of them. I'd better send them here and *then* there.
One minor thing I don't like: A really poor AI. Everything kind of rolls over and dies when you get even a little advanced. At the civilization level, I've found the best strategy is to grab two spice mines early, build turrets on my city, horde troops, and -- when attacked -- send them full force to the opposition's city. The AI folds up the attack and tries to defend themselves which wastes the advantage.
Another thing I don't like. At the civilization level, there's a point where, if you horde enough cash, you instantly win the stage. Really. Like you click a button and bam! You win. The AI doesn't have this option. I shouldn't have that option either.
The creature creator is neat. I need to spend more time *coloring* my creations (even though there's no strategic advantage in it). I spend lots of time making them look cool in spite of the fact that they're all white though. 8)