The new feature to run multiple sites on one web instance and database is working now and will be in the next release. You can check it out now using one of my 3 demo sites :

demo.mojoportal.com
demo2.mojoportal.com
demo3.mojoportal.com

All 3 sites are being served from the same folder and using the same db, though they all have completely separate users and content.  I've configured them each with different skins to make it easy to tell them apart.

demo.mojoportal.com is the root and admin site where you can see how the host names for the other sites are configured by clicking the Admin menu after you log in. You can even change the skins on the other sites from demo.mojoportal.com.  I do have separate Virtual Hosts for each site configured in apache, but they all point to the same folder.  Having multiple Virtual Hosts in apache is not neccessary for it to work if you have the site configured to respond to all requests on the ip address, but I need them to host multiple sites on the same ip address including but not limited to these 3 demo sites.

Feel free to login as admin on these sites and play around, they all use admin@admin.com with the password admin