To me, there are two places where the ebook will win over a dead tree book, any day:
1) Whilst reader is prone (in bed, lounging by the pool on holiday etc), and ebook is lighter than most paperbacks and it is requires no effort, if bored of the one you are reading, to switch to another one (no need to get out of bed, find the book, get back in bed etc)
2) Whilst on public transport, especially trains. If you have to stand (which is a regular occurance on commuter trains) you can still read to pass the time. I always found it really inconvinient to try and read a dead tree book whilst stood up, I constantly lose my place, drop the book etc.
Where they lose out is that you don't have to remeber to charge a dead tree book!