Luckily they got mostly positive reviews, however most apps have their reviews and comments trashed. I've seen great, 5-star apps go down to 2-stars because of people who downloaded it because it was free, didn't know what it did, then didn't like it and give it a 1-star. Others give 1-star because amazon screwed up and charged them, others give 1-star because it doesn't work on their device (even the description will say it isn't going to work). These things wouldn't happen with when people find the app and choose to purchase it.
The complaint seems to be that Amazon is talking out of both sides of their mouth. Telling the public that developers are getting 20% (thus making people feel good about installing the free app) then asking developers to agree to a rule change and accept nothing instead.