I was so confident about new iPad mini being announced on Apple September Event, that I sold mine the day before keynote.
As a result, I'm left without anything portable yet big enough to be comfortable for reading. And, since time has proven that I used iPad mostly for reading—Kindle Paperwhite was easy decision.
First things first. You can not compare Kindle Paperwhite or regular Kindle to iPad. Only thing those devices are capable is reading, that's all. But, boy they are good for reading.
Kindles come with e-ink screen. Benefit is literally no glare in any lighting situation and outstanding battery life. Because of backlight, Paperwhite is bit heavier and thicker than regular version to provide near-equal battery life.
Patented backlight is Paperwhite’s highlight. It works, but it is a bit odd. Amazon recommends to use maximum brightness in daylight and near-minimum in dim or dark situations. Personally, I see no reason to use backlight in good lighting whatsoever. When backlight really shines is night. You could read Paperwhite in absolute darkness and not disturb your beloved one, sleeping nearby. Sadly, backlight is far from perfect at lower levels. You can clearly see 6 spots of intense light (LEDs that provide light) in the lower part of the screen. Rest of the screen is evenly lit, but those spots are sometimes annoying.
User interface is another huge improvement from regular Kindle. It has slightly higher resolution touchscreen which is responsive enough to keep up with slow e-ink screen and precise enough to use it actively when you need to look-up for a word in a dictionary. Only thing I miss are paddles for page turns as on regular Kindle. I find them way more comfortable than swiping or tapping on screen.
Amazon services were always very good and reliable. Thus, managing your library, sending files to Kindle Cloud and purchasing books directly on device are very easy and comfortable. Things I would love to see in future is built-in Instapaper and RSS reader (even without on-device feed manager). That would be truly fantastic.
Kindle Paperwhite is one of my favorite product at the moment. No other device is as comfortable and pleasing to use for reading as Paperwhite. It is sad Amazon is using same name to sell its iPad rivals—Kindle Fire series (including just announced HDX and HD). All of them, in my opinion, simply can not compete with Paperwhite for reading, and with iPad for everything else. iPad is still king of all tablets by a huge margin because of eco-system and performance combination they provide.