I own a Fred Perrin's "griffe" (a somewhat different model), that I carry around my neck when traveling by car around the country.
Good design, good quality.
As others have said, it sure is a small blade, but for defensive purpose it will do the job.

As for using it for other purpose, why not ?
I don't use it to open cardboard boxes, because :
- it's too nice a (custom) knife to use for such a menial task ! ; <img src="/images/graemlins/smirk.gif" alt="" />
- the neck carry principal advantage is discretion, so I won't get the griffe out of its hiding place on trivial occasions.

But I did use it once in a relative's kitchen to cut some meat for cooking (his kitchen knives were in such a poor shape ... !!!!). <img src="/images/graemlins/cool.gif" alt="" />