Looks like Cablevision is the first and only US cable provider to sign up (so far):
From the article
"Cablevision is the first U.S. cable MSO to join the Netflix Open Connect content delivery network, which also includes Mexico's Telmex, Canada's Telus and Virgin Media and British Telecom in the United Kingdom. Netflix says it doesn't charge ISPs in the program fees to receive its online video programming directly at interconnection points.
News of Cablevision joining Netflix Open Connect comes less than one month after Netflix announced that Netflix subscribers who are customers of Comcast (Nasdaq: CMCSA) and Cablevision rival Verizon (NYSE: VZ) see download speeds for Netflix TV shows and movies that are faster than those delivered by Cablevision and other broadband providers."
reply to vandergraff2
Basically, SuperHD is just the old X-High/HD that they are now limiting to their own CDN. A month or so ago, they re-encoded the HD to use a lower bitrate (High/HD), but said it should look as good as the old X-High/HD. Without side-by-side comparisons, I can only assume they are using the new encoding at higher bitrates that should supposedly look better than the old X-High/HD.