just to chime in...i've just had my first two exams and did MC first on both....and even though I feel awful about the essays, i feel really good about MC. Just what everyone is saying here--it's a quick confidence booster, there is an answer--and they've printed it out for you, etc.
But if you have the whole exam time to do both, do try and finish MC quickly so you have more time for the essays. Leave MCs you don't know for the end, if you have time. I wasted too much time on single MC questions.
Of course, I have no grades, as of now. So maybe my system sucks.