This was pretty much an impulse buy for me and I was bit worried when I first started it up, given that I'm not a fan of real life horse racing. I'm completely addicted now, however. There's just something compelling about it (the "just one more week" factor) and it's a nice change of pace.
I really enjoy the tactical nature of the races and and like the fact that it's possible to understand why I'm winning and losing, even though I'm still losing most of the time. The stable management options aren't that deep, but they do the job without over-complicating things.