Using the Cloud isn't only about instant scaling and per hour billing. Those are useful features, but mostly for specific use cases.
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The Cloud it's about the ability to have software that controls the hardware.
It's about being able to orchestrate automated failovers that provision new servers.
It's about being able to have services that grow and shrink depending on usage.
It's about being able to replace your app servers with data crunching servers at night and relaunch new app servers at day - all transparently.
Of course, those are just a few examples, but the general idea is that programmatic access (APIs) is the big thing. The rest is secondary.
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Is is, however, true that this is not useful to everyone.
On the topic of succeeding using the Cloud, it's indeed difficult. That's why companies are building cloud management tools to help users do this.
Disclaimer: I work for one of these companies.