I only have the trial version(because I did not want to spend $10 on the full version), but it's still amazing.
Though perhaps not in the way that it was intended to be. Given the few types of body parts available in the trial version, I have been "forced" to create some very freaky and one-sided creatures.
I started out making a few regular, normal looking creatures, such as the Genericosuarus mongoliensis. Eventually, I began turning to works of fiction for inspiration, making some very pokemon-like things. The bee thing actually turned out pretty nice.
But then, as I became more aware of the effects that various body parts added, I began to create mutilated monsters with six mouths, eleven pairs of wings, and so on. Limbs began taking on more than three joints, creating freaky muscle-spiders. Spider goat, spider goat, does whatever a spider goat does...
I do have a few less hideous monsters though. I attempted to reconstruct the Taxxons and Hork-Bajir warriors from the Animorphs series. I think I did alright with the Hork-Bajir, considering my limited resources. Sure, the beak was sideways and he looked a bit too cute, but a fan of the series could probably identify it. The Taxxon, on the other hand... Well, he looks like turd.
The freedom that the Spore Creature Creator gives you to manipulate limbs, delete parts and combine others, is such that even without a large variety of different types of limbs available, some really cool things can be achieved.

Now, imagine an entire planet of those. Better yet, imagine them getting onto spacecrafts and colonising the universe.
The Spore Creature Creator is the sandbox of the future. From a simple lump of clay, of a very limited size, one can produce so many interesting and hilarious creatures.

And this, all before the actual game is out.
-Joe