I will never understand the whole virtual machine and cloud craze. Your operating system is better than any hypervisor at sharing resources efficiently.
Automatic scaling is great. Cloud parallelization (a.k.a fork) is absolutely wild once you get it rolling. Code deployments are incredibly simple. Never having to worry about physical machines or variable traffic loads is worth the small overhead they charge me for the wrapper. The generic system wide permissions model is an absolute joy once you get over the learning curve.