Guys who think it screws PCs: It didn't screw my PC, and mine's a pretty old 2005 one, and it's a laptop...
Make sure your PC has a graphics card thats more recent than say 2004, since if it's from earlier than that, Spore might reject it...
Tamaw/pants: What you do in the game? It's everchanging as you evolve.
You begin in the cell stage, a 2D thing where you swim around and eat whatever's smaller than you, and run from what's bigger.
In the creature stage, you're an animal and you can make allies or enemies with other species and eat either fruit, other animals, or both!
In the tribal stage, you've formed a tribe and indirectly control your villagers by giving them orders. You can now use tools like instrments to aid you in allying with other tribes, weapons to kill other tribes or food to domesticate animals you can use for eggs.
In the civilisation stage, you've made tanks, planes and ships and a city, ready to battle with other factions of your own race using these.
In the space stage, you pilot a starship and land on foreign planets. You can either ally or become enemies with the races there.
It's basically like 5 games in one! Definately worth it! And plus there's a creator where you can make whatever you want, the same one from the demo, plus clothing creators and vehicle creators.