TekunoRobby said:
Yes.
I was heavily addicted a couple years ago. From what I remember, there's not anything like what you could call a complex gripping storyline -- it's all about jumping from area to area, solving some minor problem, and collecting/breeding the local monsters.
It's a little on the short side -- though I remember being ill-prepared for the 'final boss' and haven't yet gone back to further breed and raise my stable to finish him off -- but once you get past that, everything the world opens up to free-play, unlocking new areas and collecting'm all, so there's definitely post-storyline lasting enjoyment.
If you at all enjoy doing the monster collection/breeding/raising thing and won't flip out over the 'dated' graphics, $8 is crazy well worth it, especially considering it doesn't appear we'll ever be getting the GBA update.