I have written a longish review article on the Editio Critica Maior, which has now been published in the excellent Tyndale Bulletin (feel free to subscribe). Some blog posts in 2007 anticipate a couple of the themes in the published review (see how big?, more thoughts, bold dots).
Here are the details: Peter M. Head, ‘Editio Critica Maior: An Introduction and Assessment’, Tyndale Bulletin 61.1 (2010), 131-152. If you are interested you can find a copy online here.
Up-date: For other NT articles in the same issue see the list with comments at Euaggelion.