I spent a not-insignificant amount of time a few years back writing poker bots. It's one of those projects that's really easy to do, but really difficult to do well. It didn't help that I dove right into coding without the benefit of having read any of the academic research on the subject (i.e. http://poker.cs.ualberta.ca/).

I will say that the time spent made me a better poker player and taught me some nifty things about AI and game theory to which I wouldn't have otherwise been exposed.