One of the main things I think developers are missing when it comes to Joomla! being a major player as a professional CMS is the poor quality and lack of SEO support. When you can't have a URL (article from a category Blog or List) without the article ID number, and no native way to add expires headers, or to bump Javascript loading to the bottom of the page (and yes, page speed quality does affect SEO), then people trying to build truly competitive online commerce sites will turn to another solution.
Incorporating things like a native CCK, multisite capability, and an incorporated backup are important, yes. But the one major drawback I see listed on most all the CMS comparison site's out there is the lack of SEO support. The current SEF URL's don't cut it. I mean,
who wants to make menu items for thousands of articles!
To be completely honest, if it wasn't for the great community surrounding Joomla when I was initially making my choice, I probably would have went with a different CMS myself, at least for the business efforts I work on.
Let's send a message to the team that the internet floats on the sea of e-commerce, and if we don't catch up to the needs of businesses, we're sunk.
Sincerely,
Aaron Wood, Creative Director
The Fresh Ink Group, LLC