That said, there are definitely some issues.
1. As others have said, the community leans more towards Drupal, and much of the official documentation references Drupal with not a peep about how to do something similar in Joomla.
2. The component is written in such a way as to generate a massive amount of php and js calls. Apparently drupal people have a way to aggregate such calls to not be such a server burden, but Joomla people don't (to my knowledge). In defense of the civicrm people they keep saying their software most likely won't perform great on shared hosting.
3. The mailing component is just ridiculous. It is so complicated to setup and is ridiculously buggy. You have to do cron jobs and all sorts of other things when there are other mailing components that do everything CiviCRM does (and more) and don't require any of this. I've setup ACY mailing in about 30 seconds. No cron jobs. No php. It just works.
One more pet peeve on the mailing. If you it the "send test email" button it sends every time. With no configuration. But I literally had to try 27 different configurations to try to interpret what in the world the documentation was talking about (again, it was written for Drupal) and even then, it is buggy. If you hit the test button and it works, the real thing should work. If it doesn't, delete the test button. It's useless.
4. The donation part of the software was useless too. Every upgrade seemed to break something obscure. Issues with php/js calls, fields disappearing, template conflicts. Joom Donation installs in 30 seconds. Configures in 30 seconds and just works. 3 freaking weeks trying to get their donation thing to work reliably only to find out that IE users were getting weird errors.
Unless you have someone whom installing and maintaining this stuff is their full time job, I would stay away for now. It was literally my full time job for 3 weeks. I would get sooo close to everything working and then I was constantly chasing down bugs. Over and over. You could do pretty much everything CiviCRM does with $100 worth of extensions and save yourself a lot of heartache.