Somehow, I have gained the impression that Creme Fraiche from the Normandy town of Isigny is the best of all. The only other thing I know about that particular town, never having been there, is that Walt Disney's last name is derived from it. According to Ian Fleming, that fact interested James Bond when he was reading up on genealogy in order to infiltrate Blofeld's mountain lair in "On Her Majesty's Secret Service".
For a very long time, I viewed Creme Fraiche as something inferior. Perhaps this resulted from our inability in France to find fresh cream; instead, it was always soured.
It always seemed to me that its sourness made it inferior to ordinary cream. Now Creme Fraiche would be one of my trio of essential creams: the other two being double and clotted. All the others - single, whipping, extra thick double - have no virtues that the trio lack, and a number of weaknesses. As Nigel Slater points out, extra thick double cream comes with a disagreeable, slightly chemical flavour. He goes so far as to say he wouldn't feed it to his cat. I would agree, if I had one.
Creme fraiche then: excellent eaten with a spoon, its richness offsetting the sourness and vice versa. But its main purpose, in my view, is as a cooking ingredient. Nigel Slater suggests adding it to a pan of cooked chicken thighs for an instantaneous and rather wonderful sauce. I agree. The cream melts into the frying pan, merging with the meat juices. Maybe add a few capers or some of those green peppercorns in brine.