I received 2 November Jupiters yesterday that are both hashing at 670ghs on average at BTCGuild with a LOT of variance. The 72 hour graph fluctuates between 640-711ghs. My Oct Jupiter has much less variance at 560ghs average.
I'm seeing the same thing, but I thought it was normal due to peak network congestion and packet latencies. Mine goes from 649 to 709.