Because of their Mesomania, BOMC is unreliable; i.e., contrary to the Church's position of neutrality, BOMC continues to promote exclusively one theory of Book of Mormon geography, which unfortunately includes the "two-Cumorahs" theory which is based on the premise that Joseph Smith and Oliver Cowdery were ignorant speculators who misled the Church about Cumorah being in New York. Mesomania infects BOMC's editorial choices throughout the web page, their selection of articles for their archive, etc.
Despite their Mesomania, however, BOMC has some excellent resources that I encourage people to use in their studies. Most important, they provide access to Royal Skousen's invaluable work on the Book of Mormon text.
Here's an example. This "KnoWhy" includes a phenomenal graphic:
Here's the graphic:
Other KnoWhys are less useful because of Mesomania.
For example, this one.
BOMC's Mesomania relies on the premise that Oliver Cowdery, Joseph Smith, and David Whitmer misled the Church for over 100 years by claiming Cumorah was in New York. According to BOMC, modern LDS scholars know better than Joseph, Oliver and David. In my view, BOMC does more to undermine the reliability and credibility of these men than anyone else, because BOMC purports to represent the best of LDS scholarship on the Book of Mormon.
This is all to say, definitely use some of the resources of BOMC, but be careful. Very careful, just as you should be when you consult FairMormon, BYU Studies, the Interpreter, etc.