I'm curious what anyone with experience about ownCloud thinks about the following...

I'm interested in using ownCloud to replace a company file server... but I'm a bit put off by the user-first file management method. It seems like a user creates and owns the files (in the data directory), but can there share them with a group... is this the way to manage a group file server in ownCloud? The share is actually stored under the original user who created into, even when shared with a group? It just seems like the approach is about managing your personal files first, and it's more of a share-some-of-your-files method than really setting up a group-first system.
If I wanted to run ownCloud for multiple clients, would it be best to run totally separate installs? Or separate users with groups under one install?