I have worked with SAP Portal and Oracle Portal. And you know few of the people who worked on them had a good word for them....
Let me explain. A portal is supposed to be an easy way of getting content onto the web, in a controlled and safe fashion. The problem is that Frontpage is easier with a little coaching, and raw html is more flexible than what the portals tools allow. The amount of time trying to get your site to look how you want it multiplies by a factor of about 5 on both Portals.
Development on both portals is supposed to be quick and easy, but trying to get that extra 5% functionality always takes 30% more time, so you lose the advantage of a proper development environment like .NET or PHP.
Portals seem to fail more often than an old fashioned web server. I theorise that this is because they are often based on J2EE and that many people loading many pages packed with many portlets (Oracle)/iviews (SAP) cause the J2EE foundation to crash. We have had a lot of trouble with our portal in BigCity Yorkshire.
Personally I think an organisation is always better off with a good content management system which sits on top of a number of technologies, and which allows those technologies to be mixed, matched and mashed.