[jaylevitt]

There are also the network benefits (pun intended). If the rest of your app does benefit from elasticity, you've had to choose betwen:

1. Keeping your app on EC2 and working around the lack of high I/O options 2. Keeping your app somewhere else and working around the lack of EC2-style elasticity

In TFA, Netflix had chosen #1, and they used to run an extra memcached layer + I/O on 48 instances. They were able to bring this down to 15 I/O instances with no intervening cache, and lower overall latency.

That said, I'd guess the on-demand hi1.xlarge won't get a lot of usage; I imagine they offer it just for orthogonality's sake (all other instances are available both on-demand and reserved), plus the ability to try before you buy.

What's really exciting is that Amazon clearly recognizes their lack of good I/O solutions. Maybe we'll see a whole range of options stem out of this... one can hope.