I went to a montessori school for 10 years and i fail to see how a system where you except a "slow" child to want to learn subject that it find difficult and put in the time, dicipline and efforts into it. The method is all about children wanting to learn subjects that are difficult and challenging for them by them self with very little structure and minimal interferance.
On the other hand, it's really visible that the method doesn't work for everybody.
So, I think that "it's for gifted children" is the wrong conclusion here, but there is something to discover on that line.