In a few weeks, it will be four years since Mac OS X 10.4 Tiger was first released. That was the first release to include Core Data. It will also be about one and a half years since Mac OS X 10.5 Leopard was released, with significant enhancements to the Core Data API.
It’s pretty safe to start using Core Data in your applications now. You certainly don’t need to wrote directly to the low-level SQLite API any more.