With adult eyes it seems over-engineered, but I still want to ride it again just because I want to support whoever thought that was a good idea and managed to convince enough people to build it.
It surprised me to see they didn't simply use retractable railcar wheels like the railroad maintenance trucks, which is apparently a fairly standard "road-rail vehicle":
Alignment could be easily automated today, or a low-tech mechanical guide mechanism could be added for the bus.
I'd expect the maximum comfortable speed to be substantially higher than the guide wheel approach. That guide wheel design seems better suited for aligning the rail wheels than continuous operation.
I travelled along the O-bahn for most of my childhood/uni years and I think it's a brilliantly simple system.
Stick a couple of guide wheels on a bus, and you've now got a safe, fast, relatively low cost transport system, that still has the flexibility (once it exits the track) to go where ever it needs to go.