I only used one, but both of us were carrying two. The main couloir and the exit from that to the ridge could be time consuming if it were in thin conditions with one axe - not unclimbable by any means though.
Long, serious and very committing route; agree with Jon here and also wouldn't take a novice...
In reply to Chesher cat: That line of the route in red is awe-inspiring, as is the overall view of the South (Italian), side of Mont Blanc. This is big, remote terrain, astonishingly fierce. Just to get to the Eccles bivi huts to launch is a route in itself, while they are in a very serious position - and pretty hard to find in poor visibility.
Regarding the novice .... as others have said.
FAO Martin - it still doesn't inspire me to try Mont Brouillard! Or the Pic Luigi Amedo.
Another face of Himalayan proportions and aura is the East face of Monte Rosa, from (I think), the Italian Macugnaga valley.
I remember walking into the cirque beneath it on a cloudy day, hard going on a not particularly well made Italian path (for the previous few days, I had been in trainers on manicured tracks in the Swiss Engandine). Beneath the face, the cloud gradually rose, revealing precipice towering over ice-cliff over buttress, higher and higher into the sky till the belayer's neck became unbearable, as the vast face reared ever higher and ever more awe-inspiringly into the sky, cloud remnants still swirling threateningly around it.
It was an extraordinary sight, especially as it is easily accessible from gentle domesticated valleys.