I think Akamai's CDN is still faster then Amazon's (especially here in New Zealand), and is one flat rate rather then Amazon's rate which increases outside of US/Europe.
Also Rackspace's control panel is much easier to use then Amazon's (In general I don't like the AWS panel, it's takes a while to get the hang of it, especially teaching a newbie is a nightmare) I can't say much about the API, but I'm guessing Amazon win's that as it is the standard.