Did it in temporarily when my Magura Louises bit the dust. Slapped a Avid mechanical disc on the front, V on the rear. Worked great. Eventually went dual disc (new rear triangle was required, broke that a week later). For most use, nothing wrong with disc on front, V on rear. Survived a trip to Moab with that setup, so it works.

chelboed wants you to use the search function. I didn't before posting and you probably should as there's likely plenty more out there on this subject.