In reply to climbingrev:
Are you thinking of a summer or winter ascent cause in early May it could be either or mixed depending on how winter's been and what the April weather will have done.
There's a webcam that gives views of the North Face of the Ben which (when the cloud's not down) shows you the amount of snow. I looked at it every day before doing Tower Ridge in early June as a summer route a couple of years ago, I think it might have been a bit spicy in early May.