MonoX pretty much runs the whole site..
all the web part management is handled through MonoX.
We used all kinds of MonoX web parts all through the site, and we even wrapped our web parts into MonoX web parts by inheriting the Monox Web Part class..
This enables us to drag and drop them pretty much if we want although we like to hard code them most of the time.
We use MonoX to handle user registration / and user management for the most part as well.
Our profiles where originally built off MonoX profiles but since then we have completely customized them.
MonoX has a whole lot more coming in the way of profiles from my understanding.. but for now I had to write a lot of custom code to make these work.
MonoX handles the news sections, we find MonoX publishing system to be great!