What did it for the ones I was working on - the images... if there's a 'blank' in the DB for the image it won't seed it. If you have the product exporter 'Easy Populate', it's easy to just scroll through fast and check. If you have a 'no image' image - that's a good placeholder, but The Google does like proper images.

Have you run the Feeder in 'Debug' mode and looked at the output? Proper length titles? etc?