I just said to Tracy "I'm going to read my book" and picked up my Kindle.
I don't think I'd ever say that about an iPad – even if the reading experience was superior – because an iPad will always be a computer first; everything else is secondary. The Kindle was designed to replace books, not let you read books, watch movies, listen to music, browse the web and play games.
If you're building a single-purpose device there shouldn't be any compromises with the design, and the overall experience while using it for its sole task should always be more enjoyable than with a multipurpose competitor.
I don't want my Kindle to do more, I just want it to be better at what it already does.