I love the idea of Groups having both Lists and Diary. I am currently doing all this with tags, but it's not collaborative.
On a film page, the panel on the right reflects if you have previously logged the film. The language also changes slightly, allowing you to add a review to an existing log/diary entry. We do not show the existence of previous reviews in the "Add a Film” modal popup, so perhaps this is an area we need to address.
I encountered this yesterday. On page /user/films/diary it will display the review icon only if a review is present for that specific viewing. If the review was created using the "review or log again" link on the /film/title page, it creates a new activity under /user/film/title/1 and so on.
Perhaps the solution is to:
1) designate/flag a review as the definitive review if multiple reviews across multiple activites, then display the definitive review at the top result of the film's activity page. similar to the way Stack Overflow allows for Best Answer.
2) display the review indicator on the film and diary page if a review exists for the film among any of the activities.
What would help is further definition of the terms. a "Review" at this point is just a user commenting on a movie. Some users try to be Roger Ebert and spend 1000 words, others just want 140 characters to say what their favorite part or biggest complaint is. Both are valid. Differentiating the two (and setting a user preference of which to see on top) would be useful.