In reply to ianghogg:
Did it solo september 2014 (just about counts as summer season still...). the goutier route is probably the safest to solo from a crevasse point of view. its such a well troden route that as long as you dont stray from the path you should be fine. saying that it only take 1 person to fall through a previously solid snow bridge into a hidden crevasse! it was slightly scary on the way back down seeing how close the track goes to some monster crevasses with the benefit of daylight!
so in summary: soloable - yes
safe - depends on where your opinion of safe lies
advisable - yes to a competant and experienced mountaineer who is willing to turn back if the risks become too high.
of course the temperatures were well below freezing and there had been allot of snow that season when i did it, every time will be diferent though.