Alas, CDs which you have bought at Best Buy over the past 20 years are not automatically available for you in the cloud. Seriously though, at first glance this does seem to be a pretty decent service.
What’s odd is that the free (Lite) version only lets you listen to the first 30 seconds(!) of your songs. This sounds like the worst decision in the world as far as constraints on a Lite version are concerned. However, I think the reasoning here is that Best Buy’s Music Cloud serves two purposes: (a) storage and backup; and (b) mobile access. And from what I understand based on this post by Brian Joseph is that the Lite version offers unlimited storage with automatic backup of your iTunes library for free. If you additionally want to have mobile access to that library then you pay 4 bucks a month for the premium service. When put in that perspective it doesn’t sound too bad at all.