There are a lot of comments about EC2's pricing competitiveness with dedicated hardware. These are fair discussions and should be had, but I figure it's worth commenting that EC2 (and AWS in general) is about much more than cheap metal.

The company that I am a developer at has aggressively adopted AWS with applications using it at both the PaaS and IaaS levels. At the end of the day what we've received the greatest value from isn't an impressive "cost per compute unit", but rather a flexibility that would be incredibly painful to let go of. For example, our QA team can spin up or tear down entire environments by chatting with our Campfire bot. Our developers can do likewise using a simple CLI we built.

Granted, this isn't exactly bleeding edge stuff here... it's simply "the cloud" (apologies) delivering on the promise of dynamic, elastic environments. But it's a really, really nice promise, and at risk of sounding like an advertisement, I'll still say that AWS/EC2 has delivered quite nicely on it.