I watched this movie last night and loved it.
From the opening scene where the caricatured bumbling mainland police are foiled by the caricatured independantist locals, I was laughing my head off.
Remi the private detective from Paris is hired on a commercial matter to go to Corsica to find Ange Leoni, the independantist who happens to be on the run from police.
Many farcical scenes ensue as Remi comes up against a closed culture while Ange plays cat and mouse with the police. Meanwhile rival gangs of independantists and rival judicial organisations all vie with each other for influence and control over events with mostly ridiculous results.
I've never been to Corsica, but if you've ever read "Asterix in Corsica", you will understand what all the jokes are about, although I doubt this movie would be anywhere near as much fun with subtitles.
The deliberately thick patois at the start is only there for colour - the rest of the movie is in lightly southern-accented French.