[bmurphy]

Disk I/O performance that doesn't suck.

Let us add dev pay instances to an ELB.

More ram.

Elastic private ip addresses.

Change security groups of running instances.

I have a lot more, but those are my big ones.

[jollojou]

While it is true that you cannot add new ones or remove existing ones, you can modify an existing security group of a running instance: http://aws.amazon.com/articles/1145?_encoding=UTF8&jiveR....