After a few rates I saw "Rate NaN movies". Not good. Then it wasn't clear that I had to click on "deegr circle" to find others that matched me. Finally, I don't think that half stars add any value. Keep it simple.
I found half-stars rather useful; they made it more natural to quickly give an appropriate rating. I frequently find that half-stars make me less inclined to over-rate something; 4.5 contains mostly stuff I would otherwise have rated 5, and 3.5 contains mostly stuff I would rated 4, as well as a few things I would have reluctantly rated 3.