I love Evelyn Waugh's writing and have read a lot of biographies and critical works plus seen various films and TV adaptations. I only found out about this film recently and bought the DVD on Amazon.
On the basis of the various reviews, I approached seeing it more in the sense of duty to tick it off rather than from any expectations. However, I found it both enjoyable and reasonably faithful to the book. Yes, it is a bit labored in places and unnecessarily updated to the 1960s. But I think it catches the essence of Waugh, particularly the way that certain characters keep on reappearing in new guises..
The main characters were captured just right by a great cast of British actors.I would pick out Colin Blakely as Solomon Philbrick, Leo McKern as Captain Grimes, Robert Harris as Prendergast, and Donald Wolfit as Fagan. Genevieve Page is an enchanting and manipulative Margot Beste-Chetwynde. And Robin Phillips played Paul Pennyfeather as he should be, a lightweight and naive person who allows himself to be buffeted by Fortune.
It will be interesting to see the BBC version due to be released in 2017. However, this 1968 version has been undeservedly forgotten and is well worth watching.