When developing tools that depend on relatively useful IaaS APIs it becomes blatantly obvious which providers fail to provide the necessary APIs to perform the fundamental tasks required to build cloud tools and applications. It also becomes very frustrating when a provider claims to be something it clearly is not.
Rackspace does not support public key authentication out of the box, which is something so fundamental to the way cloud developers work, that it is difficult to consider Rackspace a serious cloud provider.
If you say you’re running OpenStack, you should really be running OpenStack with full API support…
p.s. I’m working on cloud agnosticism for CloudEnvy, and my biggest frustration thus far has been Rackspace.