Probably all dependent on conditions. I've never done the traverse, but did check it out once from just above Whatcom Pass at a time when it would clearly have required walking below huge blocks of ice that were sitting on wet slabs. Reminded me a lot of traversing the pocket glacier approaching NE Buttress of Slesse. I also just checked Nelson Vol I, where he says "danger from falling and sliding ice." Like so many other places, probably pretty risky at some times and pretty safe at other times.
Condition dependant is an understatement! When I was there in August of '99 the blocks of snow/ice were beetle (new VW, not old) sized, and coming through about every 10 minutes. Needless to say, we didn't go for the traverse....