PRT is a good way of transportation between airport terminal, between big stations. I don't think it might be usefull in Paris replacing a subway line, but it might be usefull in little towns. I've read a lot about this new way of transporting, and it's not expensive and it could work in certain cases, for example, to get from the station to downtown, or any industry.
I think we shouldn't try to construct this in such as big cities like Paris or Buenos Aires, but I think it could be very usefull connecting airport terminals, or train stations.
Ters, again, I'm not thinking this in terms of big cities or with too much stations. Imagine this: Any station in the south of your city with (let's say) 20 stops, and in another terminal you add 20 stops too, you draw a personal car lane, and you buy mini-vans with a capacity of 25 passengers, they all must full it's vehicles, if not they won't go to the next station. The system just uses what it's neccesary, plus the system will never fail, and it's not expensive.
I think that in several cases, this could be a perfect solution. Of course is not a very PRT, but I took the idea and i'm trying to make it work in simutrans. Thanks everyone for your replies!