We've been using CCK extensions almost as long as we've been using Joomla, but we're seeing a really positive evolution lately. As the Joomla! content component has improved, there has been less that we needed CCKs for.  In tandem to this, the Joomla! plug-in architecture has become really useful.  So rather than replacing the Joomla! content component with a whole extra user interface, we can extend it, adding our fields data as required.  The solution we've been using for the last year or so is FieldsAttach which allows you to augment the Joomla! content editor with fields of your choosing.

There is a great overview of CCK and FieldsAttach from Brian Teeman's presetation at Joomla! Day Germany 2014.

An alternative is fieldsandfilters.