You can find some good reviews here:

There are quite a lot of people complaining about the small screen size, discomfort for long reading, no wireless access and no access of Kindle store for instant download of books and newspapers when reading on iPhone. If you only use the device for reading occasionally then it should be fine. But if you’ll use it for reading often then it is the best bet to buy the Kindle 2. You’ll definitely feel a big difference on the reading experience.

The actual customer review on Amazon should be the best place for you to explore. It is the most informative place and you should be able to make up your decision there:

If you already have an iPhone, the 360-400 dollar expense to get the Kindle 2 may not be worth it. Here is what you get (or not get) with the iPhone:

- Newspapers, magazines, and blogs is not available.
- Can’t search, make notes, or highlight text.
- No text to speech
- Smaller screen, obviously
- Shorter battery life

If you can live without those things, or can’t imagine plopping down that much money, get the iPhone version.

do not spend your money!!