Summary: Amazon has a pretty good setup for publishing to the Kindle. He's sold roughly a copy a day since August for a couple of bucks a pop. He seems rather upbeat about this.
Regarding feedback, however, my experience on Scribd and the original message board I created during serialisation in 2004 was lackluster. It's one thing to read - another thing to make the effort to contribute constructive feedback effectively.
I'd also point out that "people buying" does not mean "people reading". Still, we writers will always live in a world of optimism in that regard.
I made my hardcover book available for sale on the Kindle, and have had rather poor results in terms of sales, even at a pretty low price point (~$7.49 after Amazon's discount). As a publisher I'm not really impressed with the market's reach. I've made more money through OverDrive's encrypted PDF e-book sales to libraries, actually, though it gets considerably less hype from the media. On the other hand, at least Amazon pays its bills, which is more than can be said about the rest of the publishing industry.
