I think reviews are a great idea, I mean , that's how I know when to buy a book, i read reviews. Anyway, I would say some good things to write about in a review are:
1.what the tickler/ticklee looks like, maybe they look like someone famous or something, are they a girl next door? what is the ticklee wearing? is the guy wearing a mask/or costume?
2. the angle of the camera, do they get good shots, are they using multiple angles?
3. expressiveness of the lee, does he or she do anything unexpected? are they a laugher, talker, or screamer, etc?
4. is the ticker good? what techniques do they use? do they add to the scene or are they a distraction? do they banter, tease, or talk to the lee?
5. what areas are tickled, obviously,
6. is it a satisfying clip? or does it leave the viewer wanting more? how does it compare to other similar clips(either by that producer or others)?
7. what kind of tickling is it? playful, sexual? both?
8. would you buy from the clip store/producer again?
9 is this a pure tickling clip or is some other fetish thrown in. i know a lot of people would want just a tickling clip and not tickling + foot worship, for example.
Hope that I helped. I have been toying with the idea of writing reviews too, so I think of questions like this all the time.