That can be awfully hard to calculate, especially with so much "cloud washing," companies offering services they call cloud that are actually thinly-disguised versions of older offerings, going on. Research firm Vanson Bourne suggests you only call an offering cloud if it's available on-demand and self-service, and if pricing is scalable, elastic, pay-as-you-go. Many companies that think they're buying "cloud" are, for instance, paying regular rent on storage they're not using. That's not cloud. OSIntegrators, a Durham, N.C.-based consultant, recently tried to deploy a file on a number of different cloud platforms and posted the results, on its Web site , including screenshots. What the exercise shows is that cloud is not yet easy, and price is not yet the only metric you need to use. So where does that leave us? At the start of a long and bumpy road. Customers know what to expect from public cloud services, and some companies are starting to meet those demands. This is a market with leaders and followers, with a few big players who've got game and a lot who just talk a good game. If you're looking to buy public cloud services, or move your enterprise computing system into the public cloud to save money, 2013 shapes up as an awfully interesting ride. If you're an investor, know that roller coasters and hurricanes can also give you awfully interesting rides. At the time of publication, the author was long IBM, GOOG MSFT and RHT.Follow @DanaBlankenhornThis article is commentary by an independent contributor, separate from TheStreet's regular news coverage.