I got one a few years ago and it was a good move for me, career-wise. I'd say the best time to do it is either if you want to switch focus in your career, or if you want to upgrade (ie you feel stuck at your current position). I wouldn't go for one if you're happy with your current job and pay, but then again, your decision. All I can say is that if you feel you need a significant change (new position, better salary, different industry focus etc), then an MBA may be the answer