Also I would like to shift my development form Visualforce to Lightning. But API access seems to be a challenge: How to call a Salesforce REST URL from Lightning Component?
CSP is blocking the access and I'm not clear about the future perspective on this.
MartyC. found a workaround, which bypasses this limitation via APEX. But if my understanding of Dougs answer is correct, this path is open unintentionally and is likely to be closed in the future:
So as a consequence Lightning Apps can best case try to get indirect API access. If the API access is turned off on purpose for security reasons, indirect mechanisms could also count as "hacks" and might be prevented later.
Are there any plans to open up Lightning API access in the near future?