I use WordPress as my blogging platform (it’s obvious). I also use WordPress default theme. And minimal set of extension, only two extensions installed currently. Google Analytics and Send email.
I have a reason why I chose WordPress and why I want to use default functionality as much as possible. That reason is maintainability. WordPress is updated from admin-interface in seconds. And if I use default functionality, problems that might happen during upgrades is minimized. And last but not least, I don’t want to spend time to find good extensions and I want to focus on content and other activities (like writing new science fiction stories from the Strangers’ Universe).
So far, I’ve been happy with WordPress 🙂