I watched the anime first and didn't start reading the manga until quite a while later. I remember being pissed that the anime ended like it did, and I couldn't stop reading the manga once I had started. It was just that awesome (though I was always a manga > anime person). I think I've read to the 33rd installment or something like that.
I don't think it was that big a shock to me though (still a shock, but not that big) because I had always been suspicious of Griffith. There was just something about him that I didn't like.