I have a Kindle; never had any other liseuses (did I get that right?) to compare it with. My observations, then, for what they're worth:
1. I really, really like being able to look up words in the dictionary. Countless times in the past I've either tried to guess at a word's definition by context--or failing that--just kept on plugging. I don't know if you can do this with other readers, but with the Kindle, you "select" the line that contains the word you want to know more about--could be definition, etymology, pronunciation--and then you click "Lookup" and there ya go!
2. A sort of related feature that I think is unique to the Kindle and that I rarely see mentioned: you can search on Wikipedia. I don't know how many times in the past I've wanted to know more about some topic and made a mental note to look it up on Wikipedia the next time I was at my computer. And then of course, promptly forgot
. With the Kindle, you can "Search" in Wikipedia. Not quite as convenient as dictionary lookup above, but still wonderful.
3. For me, the button thing is WAY overblown. While you're actually reading, it isn't a problem. When you're handling the thing at other times, you put it to sleep first, then brushing the buttons doesn't matter.
Hope these are clear--I'll be glad to answer follow-up questions if not!
Regards,
R.L.