Just so you know, I didn't like the show at all at the beginning. It took me quite a while to realize that I did like it (like after I had finished the series).
Weird, I don't think I've ever had to watch through a whole show to find out I liked it.
FMA: Brotherhood - 8 episodes and it became an uber addiction
Avatar: The Last Airbender - About 1 season to become a lifelong obsession
Doctor Who - About 3 Matt Smith episodes and I was hooked(and watched the whole series from the beginning, twice)
Legend of Korra - About negative 2 years, since that's when it was first announced. :b
So if the show doesn't get me by around episode ten, I might just leave it be.