I played it on day one, but I hadn't really caught any hype until the last couple of weeks leading up to the release, so I never had any idea of what the game at one point was supposed to be like.
I didn't hate it, but it felt like it lacked substance and probably wasn't worth the $50 I paid for it. Mainly, as a lot of other people have stated, the tribal and civilization stages felt like watered down, underwhelming versions of other, much better games. I also remember the space stage feeling messy and broken, though to be fair, maybe I just didn't get it. The most fun part of the game by far is the first and second stage where you walk around trying to evolve your creature and play around with the creator, but that's just not enough to redeem the whole game.
It felt basically like of those mini game compilations where you get one pretty fun game and four ones that seem rushed and don't really work as intended.
Also, let's not forget: a big part of the reason Spore was received poorly at launch was because it was one of the first cases in which a game implemented really poorly thought out, way too restrictive DRM. Only being able to play the game while connected to the Internet and only being able to install it three times seems harsh even by today's standards, imagine how it came across back then...