I have a US dispatch license and can offer some info on the course.
I studied full-time at the Sheffield school of Aeronautics in Fort Lauderdale and got the license in six-weeks. The course is expensive but I gained a lot of valuable industry-specific knowledge that has definitely been a great benefit in my work as an ops controller and now as a pilot (gonnabe-type).
The course includes Met (a LOT of Met, almost half the course), flight planning and other factors to be considered in flight planning (MEL, CDL etc). The job of Dispatcher in the states is very much more involved than it is here in Europe. The dispatcher generates the flight plan and also checks it for mistakes and compliance with both met(There have been many occasions in LGW where I have seen aircrew handed a flight plan together with a met report showing the alternate or sometimes even the destination aerodrome below minima) and MEL/CDL.
Once the aircraft is dispatched the dispatcher remains responsible for the flight watch of that aircraft and is in touch with the aircrew by company frequency throughout the flight. He or she is involved in any decisions regarding diversion and may even instigate diversion if weather becomes a factor during the flight. As such the dispatcher is a vital "extra crewmember" available to advise the aircrew on decisions that have a bearing on safety and also on commercial matters, relieving the crew of extra workload and allowing them to concentrate on the important matter of flying the airplane.
The value of the license in Europe is not so clear. IMHO there is a definite need for this kind of support for the cockpit crew, particularly given the workload that the two pilots at the sharp-end have to deal with in Europe´s congested airspace, however there is not as yet any requirement for it. The license, ot more specifically the knowledge I gained, has helped me to better understand the technical decisions which pilots make and made me a more effective ops controller. Furthermore, now that I am flying I find that the knowledge I gained in those six weeks has given me a stronger foundation in general aviation knowledge on which to build my career.