Be careful installing this game! The first time that you run it, Spore will tell you that there are patches available and ask you if you wish to update the game. DO NOT SAY "YES!" Once you patch the game, you will be unable to register it with the key that you download with the game. Say "NO" to the update dialog, and the game will then let you enter your key to register it. After you register the game, it will start normally. At that point you can quit and re-launch. When you relaunch, you will be asked again if you want to update, and this time it will be safe to say "Yes." The game will download five patches in sequence (you have to say yes to each of them), and apply them. The whole patching process took me about 40 minutes and finished up with a fully updated, playable game.
If you already patched before you registered, the game will quit at the initial splash screen and refuse to play. You can fix this by uninstalling the game (delete the ~/Applications/SPORE directory and the ~/Library/Preferences/SPORE PREFERENCES directory). Do NOT delete the Spore.dmg or keys files that you downloaded from Amazon, you need them to re-install. Double-click the Spore.dmg file to re-mount the installer image, and run the installer again from there, following the cautions in the first paragraph. You should be good to play then. (I ought to know, I had to run through this process on two different Macs.)
The game itself is okay; I've never gotten past the civilization stage. In fact, everything after the evolution stage bores me, but that first stage is a lot of fun. My daughters (7 and 11) enjoy the animal portion of the game as well, creating innumerable species. The online aspect of the game is fun, as you can register to use each other's creatures and have your friend's beasties wandering around your world. In my opinion, the game was not worth the original hype and price, but at $15 it's a decent deal. Just be careful installing it!