Jennifer, from our sibling site PreCentral.net is a recent Kindle 2 adopter and so eager is she to get her geek on the Pre and it's potential Kindle App, she decided to take the iPhone version for a test drive. What were her thoughts? Looks great! More:

I was just starting Chapter 11 in my eBook "Terminal Freeze" on the Kindle, but when the iPhone version of the book opened, it was on a different page. I noticed that I had the wireless on my Kindle 2 turned off, so I turned it on. As soon as I did that and rebooted my iPhone, a message popped up asking if I wanted to sync to the furthest page read, and of course I clicked "Yes". And sure enough, the page went to the beginning of Chapter 11. So it looks like the Whispersync works pretty good.

Head on over to read the rest of her hands on, and maybe encourage her to keep that iPhone groove going...