This keeps happening repeatedly - so let there be no more startups offering missing features of EC2. Go back! Build something else! Amazon has made it clear that you should not build a general cloud offering on top of EC2 - it must be niche, or not an enhancement of their offering, or they will simply do the same thing and kill you. And I don't think its that they're copying anyone. They've given lots of notice. Its just that their product vision fits with most anyone's who looks at what EC2 is missing.
Their "Key Features": (1) Auto-Scaling, (2) Monitoring & Alerting, (3) Load Balancing. Ouch.
But you're right -- the opportunity to provide unique value is in harnessing EC2 for specific purposes and applications.
It appears to me that RightScale is positioning itself to be a market for cloud computing services. It will be interesting to see if they pull it off.
Also, from the description of the monitoring service (i.e. no agent required) it is likely the monitoring data is collected at the host not the guest OS. So there is probably no process monitoring it follows that application profiling and similar services will not be possible with the data.
Amazon is building an entirely new ecosystem and we'll start seeing news kinds of tools (commercial and open source) built in and around it.
There are many cloud providers now. Startup should be diversifying their offerings to work with all cloud providers this will give their business the best chance for success.