Ah, that was my trip report that Bensta commented on!
Though I have very little experience and thus entitled to only an ill-informed opinion, I'm pro ax leash. As Anton pointed out, even if you have a leash you don't always have to use it, but in some situations it can be useful. While my party was definitely novices at using ice axes, our problem was the axes getting stuck in hard ice when glissading and the handle slipping through the hands (and that happened to one guy sitting up and one guy in self-arrest position). In that scenario having a leash would mean you just get your wrist yanked and either stop with the ice ax or jerk the ax free so you keep sliding, so definitely potentially useful and probably not too dangerous there.
On the uphill climb I'm not sure how the pros/cons of a leash would play out - in the morning slush when we went it was pretty snowy outside the groove everyone was glissading down and probably not super difficult to stop oneself or slide all the way down uninjured even if you lost your ice ax, assuming your crampons didn't catch and send you into a tumbling ball of injury.
Probably getting pretty moot for this season though as conditions seem to be melting enough that you can just take the switchbacks up and down now.
