"Rackspace uses 213 of Akamai's edge locations, selected especially for our customers' typical usage patterns, and designed to cover all major areas of the globe." http://www.rackspace.com/cloud/files/
Akamai has approximately 5 gazillion edge locations, so yes, it is a cut down version. It is still a lot more POPs than just about every other CDN, though this doesn't necessarily translate into performance.