Fresh revisions of the firmwares explicitely deal with the Arduino internal 10K pull-ups and allow for dispensing of the external pull-ups, resistors, LEDs and endstop-pcb paraphernalia: a most welcome simplification.

Many microswitches come with a 10 mm spacing between M2 holes. The Prusa Mendel endstop holders feature a different spacing & hole size. Fear not! editing the parametric file is straightforward, and for expediency here is also the stl file.

Note: All due credit must be given to Adrian's Prusa Notes reprap.org/wiki/Adrians_Prusa_Notes : he deals with 9.5mm spacing and M2.5 holes. My mod was independent of his.

I adopted lever-less microswithces, they supposedly allow for better repeatability.