Lots of people don't like it, but I remember I found myself thoroughly amused by it. The gameplay is very stale and some of the in-game systems are lacking (at best), so there's a lot of room for improvement with the game.
However, if you're not going into the game expecting an action-packed blockbuster of a game, but instead expecting something where you can just have fun designing cool-looking creatures, ships, tanks, airplanes, rocket ships, and buildings, then it's worth checking out.
I'd probably have a lot more fun if the game actually used your creations throughout the game. But 99% of the creations are the pre-created creatures that were developed by Maxis themselves. It really takes the fun out when even on your 20th playthrough you haven't seen a single new creature.
Also, I'd like to point out that the sequel to Spore, Darkspore, is coming out soon. I'm in the beta and it's actually a lot more fun. They basically combined the customization and premise of Spore with the gameplay of Diablo II. If you want Spore but with a better balance of gameplay and creature editing, then just wait for Darkspore.