Incredible shrinking manual
The big change between Kindle 3 and 4 is a reduction in size. The bezel is much narrower and, as you'll have seen from the snaps, there's no keyboard. The new model is a fraction of a millimetre thicker, but feels more so thanks to a less rounded, less tapered edge.
The build quality seems decent enough.
The old generation... and the next
The new Kindle is more pocketable than its predecessor, and while the virtual Qwerty keypad is certainly less convenient - and slower for text entry - than a physical one, when you're only keying in search strings and Wi-Fi WPA 2 keys, that's no real problem. If you expect to type more than that, wait for the Kindle Touch or go for the still-available Kindle 3, now renamed the Kindle Keyboard.
I like the Kindle 4's smaller size, but I miss the Kindle 3's curves and darker looks. And the old model had bigger page turn controls. The new ones are narrower than before, so they're rather harder to trigger one-handed.
Kindle 4 has much narrower page turn buttons than its predecessor did
Amazon has given the Kindle 4 the same 6in, 600 x 800, 167ppi E Ink Pearl display it used in the 3. I still prefer it to squinting at a smartphone screen. What has changed is the refresh rate, sped up by cutting the regularity of a full screen reset - e-book readers' infamous black flash between new pages - from every page to every six pages.
Clearing the screen - turning all the pixels black - has the advantage of resetting the tiny particle packets used to shade each pixel. The cost is page turn time.
Next page: The text, the text, the text
re, converting ePub to .mobi
I think that the majority of Kindle users will not know how to do this and not even be aware that it can be done. Data format and file wrangling is a rare skill among the general population.
I have a *.epub file, then:
1) I drag it to every reader in the world apart from Kindle. Yup, that works. I am happy.
2) I drag it to the appropriate Kindle folder. Doesn't work. I am not happy.
99% of people DO NOT GIVE A MONKEYS about the tech detail. They just get annoyed because it works everywhere else but their lovely new Kindle. And that's why it's 'plain silly'.
Re - but don't expect a USB AC adaptor to come with it;
That's good. The whole point of USB chargers is standardisation, so you don't need a new charger whenever you buy a new gadget. Which sadly doesn't stop many manufacturers from bundling one.
I've got about six of the damned things. I don't even need a new cable every time.