In reply to nickc:
I'd go a bit further than Offwidth and stick my neck out and say 2 out of 3 years. I've climbed most of the variations... the best left hand route is a bit rarer to form completely - last IIRC was about 5 years ago. Normally as already stated you can get good sport at about gradeI/II starting right then traverse left to finish. A good winter should also produce a rarely climbed line left of the downfall in the ampitheatre.
There are also a few other good areas for those in the know - Torside Clough being one. (Bleaklow tends to have more areas & generally better conditions). As with all English ice an early start is to be recommended!