I watched a documentary about them a while ago, and have to say that I had nothing but respect for the guys who made it thru. They take anyone. You don't even have to speak French or English. Your (criminal) past is of little interest to them. Unless you are wanted for a major crime they will give you a new start and even give you a new name.
After this the fun really starts. The training is similiar to how they train Russian soldiers. It is brutal, unfair, they expect you to figure out french in short order, and training "accidents" are higher than other comparible Western mililtaries. You can "wash-out", but they said that surprisingly very few do. I guess it makes sense as by the time you actually sign your name on the dotted line, your mind is pretty well made up. You sign up for a five year stint and if you complete it your criminal record is for the most part erased. You are also awarded French citizenship, and a nice pension is provided.
The troops themselves are known to other militaries as an isolated and rough bunch. They are part of the western allied integrated command, and during the first gulf war they were some of the first troops to cross into Kuwait. They are often used as shock troops and put right on the front line. It was mentioned that they often had to keep them away from other military units as they would often start fights. Unofficially it seems that the French use them for all sorts of nasty little jobs in their former colonies in Africa.
There is very little that is "romantic" or "pansy" about them, and I think if you insulted one, they would probably leave you bruised and bloody in short order. Personally I would put them on par with American Rangers, or British Gurkhas. Not to be messed with thats for sure.