We dumped Rackspace for AWS. I tried desperately to get them to do anything for us about their cloud as we had dedicated servers and needed to grow a bit. I was able to order a huge dedicated server at an OK price, but FFS it took eight weeks to be available for use.

I asked a ton of times about their cloud stuff and just got re-directed back to dedicated servers. I got tired of it, went to AWS, and haven't looked back. Using reserved instances and scaling groups we're paying about 10% less per month for 8x the number of servers, and slightly more cpu/memory/disk overall (we had some pretty beefy stuff at Rackspace).