I sell portals as part of Sage CRM. It's a growing part of my business so I'm thinking Sage isn't alone in that regard.
The trick to a good portal strategy is to define what elements are portal and what elements are human interaction. When it comes to Sage U specifically (this is not the same as Sage as a whole), they seem to want everything to go through the portal. Considering there are hundreds of high quality, highly regarded self service training sites, I don't think this is an unusual or even unacceptable approach. Most people want to find their videos, pay for them, watch them, and move on. Not much human interaction required there.
No, the problem is not with the concept. The problem is that the Sage U implementation is a steaming pile of crap.