As someone who has very little experience in it, I would like to know what makes you think that Joomla can fulfill all you requirements?. What makes you choose it over development from scratch (or using a framework like Yii or Kohana).
What are the most common or crucial problem that you are facing when using Joomla? Since I don't have much experience in it, I would pressume that one of the biggest problem is flexibility. You can't scale or customize the behaviour of your app, and even if you could, you need to break some rule in Joomla, or wait for the next release. Is this true?.
Currently I am building a long term project, there might be a lot of specific functions and behaviours in it. I would like to build it from scratch or with help from some PHP frameworks. But I've seen so many websites (and some of them are great in terms of complexity) are using Joomla. This gave me some doubts about choosing the right tech.
I would like to know is there any, one or two ultimate reasons to choose Joomla/other.