The main advantage of Prolog is that it forces you to think in different ways to solve problems. The main weakness of Prolog is that it forces you to think in different ways to solve problems. Especially because most existing libraries are written in procedural style, so they don't work well with prolog. In the end you'll have some difficulty to integrate with existing code.
I always felt that Prolog is a super valuable dsl that I would wish to be embedded like a reflex for certain problems, but is I'll suited for most programming tasks.
I.e. have the GUI, Io etc. in language better suited to that.
