I think it's there now (speed and flexibility over cost), but what we're catching up with is trying to compare some performance on-premises to a cloud. In many cases people want a predicable performance because they get that often locally. They don't, and many people don't want to accept variation, so they overbuy.
I do think costs are a little high. Now they're roughly on a 2 year payback, and I think they need to move closer to a 3 year frame.
The other thing that the cloud needs is a moving set of workloads, not a constant one. The more constant, the more you can think about doing on premise, though it's not simple. Today lots of companies have an investment in a data center, so moving to the cloud makes less sense. If I've built (or rented) xx sq ft of space, and am paying people, power, cooling, what does the cloud get me? Not a lot. In the future, if I can get rid of those payments, maybe the cloud makes more sense. I think the IaaS stuff is really catching on as contracts expire and companies consider leaving current spaces, or can sell them
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