Good work. On Imsy (www.imsy.com) we hope to achieve the same with Node.js on EC2. Presently the numbers are smaller (in 100K range).. but looks like it will scale smoothly till 1 million.

It's hard to say that something is going to scale smoothly up an order of magnitude until you're there. 900K requests is a lot of room for things to go wrong.

Node has memory limit of about 140K connections. I was able to accept and actually do something usable with 1M on EC2 and 3M on physical server (Erlang and Ubuntu/CentOS)