Beautiful design, I am still planning the build of my 'next' machine, currently using a RepRap Air 2, but I am looking forward to building either a MendelMax or a Deltabot. Deltabot seems cheaper (1 less motor, and all stepper drivers are only controlling one stepper motor).
However, the reason why I want to build a MendelMax is because of the extrusions, but since this Kossel uses extrusions.. Maybe I should look into this model instead