Only that packages ending with 'A' are supposed not to be production ready. Every 'B' version is advertised as good for production. There should be backwards c

Only that packages ending with 'A' are supposed not to be production ready. Every 'B' version is advertised as good for production. There should be backwards compatibility between two major releases, but not more. You could likely go from R14B to R15B, but optimizations and bug fixes usually make it worth it to upgrade in certain circumstances and setups. I can't help you with Ubuntu, though. That's the responsibility or choice of the person in charge of the packages.