Opera - since version 15 - is based on Chromium, and is not considered as an update of the 12.x and earlier versions. It doesn't yet have all the features of Opera 12's Presto engine, but it is faster and handles problem websites better (especially web apps like Yahoo Mail and Google Docs).
Some of Presto's features - like MDI in Windows, I know Mac never had that to begin with - are not possible in Chromium. Some features (Bookmarks management) they have decided to leave to extensions - if you want it, then search the add-ons site to find one you like. I'm not sure what the status of Fast Forward is, but it may be another one they figure is better handled by an extension.
