Wait, can't you just buy an R9 270X at 425kH/s and an U1 at 1.6GH/s for $300 instead of 3 of these at 120kH/s and 1.5GH/s for $300? I don't understand the advantage of these devices. Maybe at half the price? Looks like Ebay candy to me.
If we talk about kh/usd, this usb miner is not good than gpu miner currently. If we talk about kh/watt, usb miner is far better. Also usb miner have some flexibility. You can use a beaglebone board to control the usb miner.