I'll do it like Torak and break it down by phase.
Cell Stage: Wow! Being a fan of fl0w, this phase makes me delirious with happiness. I've played from Cell to Space as both a Carnivore and a Herbivore, and being a herbivore here actually makes it slightly harder, since you don't get food (and health) from killing things. My only compaint is that it finishes too soon.
Creature Stage: it's like a slightly smaller Morrowind, only you get to customise your creature! But seriously, you get to wander all over your (admittedly small) planet, either eating or socialising with other creatures. Being a herbivore makes it easier in this stage, as food is plentiful and less dangerous to acquire. I never figured out how to pick up and give food to other creatures, however. Also, I never found flowers or seashells that are apparently able to be picked up and given as gifts. Anyway, you should spend most of your time here, trying to gather as many pieces as possible, since this is the only stage you get to create your creature. I got most of them, but I missed out on some hands and feet, as well as some detail parts. You end up with some strange-looking creatures, too, depending on whether you want to kill or socialise. Allying with creatures is really difficult, and requires parts, parts, and more parts, to the point where you just stick random parts wherever they'll fit so you can kill or impress.
Tribal Stage: Well, you get one final trip to the Creature Editor, and then that's it. Unlocking as many parts as possible is vital here - not because they really increase your tribal abilities, but because it's the only way to get some decent-looking creatures. Even so, the choice of eyes is... disappointing, at best. Anyway, this stage is basically 'build up as fast as you can and exterminate the competition.' Being a Carnivore hurts, as other tribes are ridiculously difficult to kill, even with equal odds. Your best bet is to wait until they attack you, then counterattack with everything you've got. Peaceful means, however, are so much easier - and let's face it, there has to be at least one stage where the hippies get a break. Just offer some food, play some music, and you're outta there. The outfitters are ridiculous, and aren't really designed for anything not humanoid. You might be able to get a few things to fit, but don't count on it. The negative is that you sorta need clothing to win, especially as a Carnivore. The positive is, you probably won't be looking at it in much detail for very long.
Civilisation Stage: Having not yet played Supreme Commander (I chose SoaSE instead...), my closest analogy would be Age of Mythology, or possibly C&C. Fortunately, military might is not the only way to win, and nor is it the most viable. In fact, if you want the simplest and most effective method of winning, religious conversions are the way to go (yeah, more Herbivore stuff...). However, if your enemy has more than one city, economic buyouts get you in their good books, so you can forge an alliance and win. It was at this point I was hooked (as though the Cell Stage wasn't enough

)
Space Stage: This is what everyone wants, but I gotta say getting here is a lot of fun as well. Anyway, you get to stick a whole bunch of pointless things on your ship (weapons are pre-set and can't just be stuck on in the editor). Basically, whatever you do is aesthetic only, so feel free to steal someone else's design you like and modify it a bit. Basically, the rest of it is similar to the Civilisation Stage, except there's no religious takeovers. I'm not sure what the herbivore equivalent is. Possibly alliances. Anyway, you push towards the center of the galaxy, averting ecodisasters and developing colonies on the way. Also, protecting your allies (and eventually, I'd imagine, yourself) from the Grox. They're the mysterious ultimate evil.
Overall: wait a couple months and pick it up for AUD$70 (or equivalent). It's not worth the $100 price tag, but it is a damn good game.
EDITORS:
Cell (Cell)
Creature (Creature)
City Hall (Building)
Tribal Outfitter (Clothes)
Civilisation Outfitter (Clothes)
Anthem (Anthem)
Housing (Building)
Factory (Building)
Entertainment (Building)
Spaceship
Vehicle (Land, Sea, Air)
That looks like about 13, if you count 'em seperately. I think of it as 6 if you count the ones that are actually
different. And count the spaceship as a separate editor. You could also multiply the vehicle editors by 3 for Military, Economic, and Religious (land Military, sea Military, etc).
Miscellaneous note: did anyone else notice the procedural walking animations? Just thought I'd throw that one in there. Stand on a hill and you'll see what I mean.
Also, this review is nowhere near as detailed as it would need to be to do this game justice. Great tracts of good features (such as terraforming/sculpting) have been omitted. However, like I said, it's not really worth $100, so wait a couple of months for a price drop or two before you get it. It's easily worth $70-$80.