I played with the creature creator when it came out. I wasn't impressed. No matter what creature I built, the canned animations and reactions built into Spore made them all kinda look like the same creature anyway. That was enough to turn me off of Spore on it's own. That and the dancing... ugh.
Also, from everything I've read, Spore is about as shallow as a tidepool in terms of gameplay/replayability. I've gone through several threads following people's reactions from everything on the game itself to the SecuRom DRM, and the overwhelming response is that it's actually kinda crappy. Like, seriously about a 90% negative response.
True, it might just mean that the people that like Spore are too busy playing it to bother posting about it, but the game forums I visit are populated with decent people who are are generally more likely to give praise to games they love rather than bash games they hate, so their opinions hold a little more weight with me than the rest of the internet.
The only real test of whether or not it's good enough is if you try it yourself though. No matter what I or anyone else says, you're pretty much the only judge that matters. But I will say this: Get a PS2 card anyway. It's worth it for Construct alone.