MaxCDN (subsidiary of NetDNA). They're faster, the support tools are substantially better (invalidation on Cloudfront is the very definition of "suck"), the uptime is better, and the cost is a LOT lower.

Their support for .Net isn't very good, so it took me a while to get things working for their REST services. Overall a much better product with much better support.

CDNetworks, we tested global page load times with Gomez. CDNetworks was more stable and usually slightly faster.