I've been at it occasionally, but the most I've been in is the editors, and that's for the occasional contest on the Sporem. (I managed to make Rat Fink in one of'm, even)
Usually though, when I've played adventures/the main game, with all the loading of the creations and the lagginess of the game itself such, its kinda hard. :(
Oh, and recently, I've seen a downloadable game EXE (no installer) called
Kerbal Space Program. Their editor looks similar to Spore's, and the various (failed) launch videos around the internet look hilarious. XD