phpNuke and similar community portal applications do provide a way of producing a good looking dynamic site.
They also all tend to look very much the same - basically most users tend to choose from one of a selection of templates, and because of this a phpNuke site is usually drop dead easy to spot.
The same can be said for most forum/portal applictaions, and I've lost count of the amount of times I've seen people saying 'look at my great site' only to find that they've populated a pre-programmed web application template with their own material. It never even seems to occur to many people to design their own theme for the portal.
Portal systems have a valid use but they are severly limited in some respects and totally overgunned in others, while to many newcomers they may be totally overwhemling.
As much as I admire what they can do, they teach people little or nothing about design and development for the web and I am not a fan of any out-of-the-box solution that only requires content.
It's basically one huge template, waiting for you to fill it.
I do agree that the results can look quite slick though.