IMO, a portal (or homepage) is, and should be, for visitors only. And you have to make it interesting enough to catch their attention.
It's pretty much a given that regular members will bypass the portal/homepage and go straight for the forum, so when I use a portal/homepage, it's not with members in mind.
I use it as a teaser to draw the passerby into the forum. It always contains a welcome message for visitors (which should always contain an invitation to join, along with a link to the registration page), a block for recent news, upcoming events, links to important forum sections, or pages, etc. Again, all with the visitor in mind.