There have been so many good responses already that I hesitate to add anything further, but I had a few thoughts:
1) I strongly agree with Anamama that part of the confusion might be that you are taking the idea of "work" and "academics" in a different sense than Montessori does. "Work" or even “academic work” (not a distinction Montessori would make) in a Montessori classroom does not mean solving math problems or doing a worksheet. Work in a Montessori classroom includes many things that other philosophies would refer to as play (using clay or playdo, coloring, making a snack, peeling carrots, painting, using building a tower). Montessori referred to these activities as work because she held them in esteem and wanted to underscore the importance of them. The guide uses this term with the children in a demonstration of respect (that the children are doing important activities in which they are constructing themselves).
So, I assume that what you are speaking of is pretend play. Montessori compares a child playing to an adult playing games (chess or bridge). She says, “These are pleasant occupations for hours of leisure, but they would become painful is we were obliged to pursue them at great length.” Like most people, she divides the day into work time and leisure time; most Montessori children engage in unstructured play time (both at recess and after school). Based upon her observations, she believed that children grow tired of unstructured play past a certain point and that much of a child’s pretend play is “not proof of imagination, rather it is proof of unsatisfied desires.”
My personal experience is that most children really enjoy the independent work time and that the materials really capture the interests of children. Additionally, I believe that she correctly identified sensitive periods where children really absorb information easily and that if you miss those windows, learning the same information later can be much more difficult (in general, it is much harder to teach a four or five year old their phonetic sounds than a three year old because they just aren’t as interested in doing it). That said, children have their choice of activities in the classroom. If a child really wasn't ready to do language or math works, a trained guide would identify that.
2)As to whether Montessori is "for" every child. I think it depends upon what you mean. I believe that as a method, all children can be successful and have a positive outcome in a Montessori classroom. If you mean, would every child be happiest in a Montessori classroom (as opposed to another type of classroom) or would any particular child be happy in a particular Montessori school- those questions are impossible to answer. I think Matt Bronsil answered that very well in saying that teachers and administrators are only human and may not connect with every person and meet every child’s needs perfectly. I think the method supplies the right framework and a good regulatory ideal, but people are not perfect. While this is a great place to inquire about the method or philosophy, it probably won't be very helpful in deciding where to send your child- for that you will want to visit schools in your community and inquire into how authentic the school is (Is there a three hour uninterrupted work period? Are all of the teachers AMI or AMS trained? Are there authentic Montessori materials present? Have lots of "enrichment" materials been added to the Montessori classroom?) and get a sense of how comfortable your child and your family feel in the environment. As you can tell from this site lots of people have had different experiences depending upon the actual school involved (I personally know of cases where a child has been unhappy in a specific Montessori school but was very happy in another). That said, in an empirical study in the Milwaukee public school system, children were admitted into an AMI affiliated public Montessori school by random lottery. They attended the school from age 3-11. The children who attended the Montessori school scored higher on standardized tests than the regular public school children and over half of the Montessori children were admitted into Milwaukee's top four high schools. Ostensibly, since it was a random sampling, there were children of all kinds enrolled (including spirited ones), and in terms of academic outcomes, the Montessori approach seemed preferable. In terms of creativity, the Miller and Dyer Head Start study compared children from similar populations in Montessori and non-Montessori Head Start programs and found that the Montessori children performed higher in standard tests of creativity and displayed more "pro-social" behaviors than non-Montessori children. My understanding is that similar testing has not been conducted in Waldorf and Reggio schools, so it is difficult to compare Montessori to those alternatives, but even empirically speaking (as opposed to philosophically) it seems that most children are successful in Montessori environments (and more successful in certain respects thank they would have been in other settings).
3) As to the observations of your friend, I agree whole heartedly with Matt Bronsil that one would expect different outcomes in a combined Montessori Reggio school. This could be attributable to the training or preferences of the teacher, the difference in the teacher’s role (where Montessori guides act as unobtrusive observers, Reggio teachers are more involved in offering children provocations), the social environment (children this age often want to observe and duplicate the efforts of their peers, so if one person is using the water table it wouldn’t be that surprising that others would follow suit), etc. One of the reasons that it is particularly difficult for me to imagine this combination working well is that the Montessori classroom provides children with freedom within an environment of limited choices. Montessori writes a lot about limiting the materials available to those things that are useful for the child's self development and the dangers of an over-abundance of activities to a child's concentration (she believed that having too many choices cause the child to engage in aimless activity). When considering her choice of material, she even tested the optimal quantities of classroom materials. Many researchers believe that the idea of freedom within the boundary of limited choices is one key reason for the success of her method. In Science Behind the Genius, Lillard provides numerous scientific studies showing that people (and children specifically) report being happier and more satisfied with their choices when they selected it from fewer options (and generally choose to do the activity more frequently, for a longer duration, and performed better at the task). A few months ago, Lillard wrote a great article based upon this information for Montessori Life reinforcing the warning that Montessori guides are given during their training to limit the amount of enrichment material in the classroom (and to wisely consider it’s necessity before introducing it). Additionally, Montessori materials are tools designed to serve specific purposes (they are not open ended as are Reggio materials)- there is a great deal of research (DeLoache) suggesting that when children play open endedly with objects they are unlikely to access the objects underlying conceptual and symbolic features. If children are encouraged to use Montessori materials in open ended pretend play, it may well have the consequence both of preventing the children from grasping the concept and reduce their enjoyment of it (one of the principle reasons young children in particular are drawn to Montessori materials is the precise use of them).
For a nice article contrasting the difference in Montessori and Reggio approaches, see:
http://ecrp.uiuc.edu/v4n1/edwards.html
Abigail Miller
www.bloommontessori.comwww.bloommontessori.blogspot.com