As someone brought up in an engineering background I tend to over engineer things but there are times when simplicity can be better.
The pipe on pipe scheme works well enough at least for smaller machines and the frictional damping does indeed seem to be a real advantage.
I have never been happy with taking the weight of the machine on bits of steel trying to cut into the top of a pipe so I have no experience of that and I don't intend to try it but although I use a thrust or taper bearing to support the weight I am reasonably happy to use pipe on pipe for the rest. In fact I do much as Sparweb has shown with a plastic sleeve rather than steel on steel but I just use a short bit at the bottom.
I have only built one machine with bearings alone with no sleeve bits and that one has slip rings so that I could use a control rope down the centre for a special furling scheme and shut down and I didn't want wires in the way. I wouldn't attempt slip rings without an engineered bearing scheme. That one does waggle in turbulent winds more than the ones with a more damped sleeve bearing set up but it is not an issue.
All commercial machines use bearings ( most have to for slip rings) and it would be a doubtful thing to sell commercially with crude yaw schemes but for home build you are probably best off doing what you are comfortable with.
My feeling is that a bearing to support the weight but with pipe on pipe for some damping is likely a good compromise.
Flux