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.<p>That said, I really like the CK interface and will give them a try for basic monitoring.