I tried the free developer version of RightScale a year or so ago. RS offers a slightly different service than CK. With RS, you can create scripts which run at startup and configure the instance. RS does automatic master/slave DB server failover, automatic instance creation and load balancing, etc... I'm not sure how their monitoring tools compare to CK. I wouldn't say they are direct competitors, and if they are, RS can do quite a bit more.
That said, I really like the CK interface and will give them a try for basic monitoring.
That said, I really like the CK interface and will give them a try for basic monitoring.