Besides, Netflix HD means nothing as long as the service providers are throttling the bitstream. I use AT&T, and I have a healthy downstream of 6-9Mbps, and Netflix struggles to stream beyond 480p. It shouldn't be an issue after Netflix is forced to bribe every ISP, like they recently did with Comcast.
When we had a 20Mbps connection (which was usually between 14 and 18Mbps), we had no issue running two at a time with both getting a 1080p stream. This is through Time Warner Cable.
Now we have a 50Mbps connection.