100LL... Again! said:
The problem with most GA checklists is that they are more of a "How to fly the 172 for Dummies" than they are a true checklist.
One of our instructors once made a light twin checklist longer than flighsafety's King Air checklist. It was unbearable.
Checklists need to contain items that will kill you or damage the aircraft, and anything else that improves operational efficiency, without cluttering the above two items.
If you put too many items on a checklist, people will tend to miss the important ones or get halfway done, drop the gear and forget to finish the rest.
Sometimes the culprit is a nerdy CFI who is in LOVE with the idea of airline-style operations and makes a monster checklist that ends up generating .4 of taxi time minimum.
NEVER put airmanship items on a checklist. For example: Brakes - apply.
or: When landing is assured - power to idle.
If you need a checklists to tell you that, you don't need a checklist, you need dual.