There is a good thread running over at rec.skiing.resorts.europe on "How hard are the Courchevel couloirs?" - first hand descriptions from people who have skied them and discussion of how difficult they really are. There is also a useful link to further info on skiing the couloirs and one of the posters has some good pictures showing the couloirs and his party skiing them.
I have always fancied riding them but they do look intimidating, the best advice seems to be that, while they are not that technically difficult, you want to be pretty confident on steeps due to the exposure.