A really good script - tight, light, breezy. It keeps Fletch in every scene, the basic story is very strong - it reminded me of a Raymond Chandler novel, with two plots that seem to be separate apart from the hero, then turn out to be intertwined. I haven't read the original novel so I don't know what's Bergman and what's Gregory MacDonald.
The character of Fletch is great - smart alecky, irreverent. Chevy Chase was clearly cast by this draft because there's reference to "Chevy Chase ad libs". You can handle the smart arse ness because he's up against a rich rogue of villains: redneck security people, the snobby Underhills (though this script doesn't have the introductory moment which showed the Underhills as bullying the waiter - it seems Fletch just randomly picks the name here), rich Alan Stanwyck (who is humanised by meeting his nice parents... I really felt for them!), a pushy unseen wife (who I did expect to be paid off more than she was), and most shockingly a corrupt cop (this film doesn't pull any punches about police corruption).
There are very clever bits of business - the Underhill account running gag, how Fletch gets out of being chased by the police (taking a leaf out of The 39 Steps and making a speech), going undercover as a doctor. It's breezy, bright and fun.
This draft doesn't have narration - I think that was a good addition. The supporting characters - Mrs Stanwyck, the police, Larry etc - come alive on the page. Really good work.