I have gone to e-books almost exclusively! My preferred reader is eReader, then it goes to MSReader, Mobipocket last. I've recently upgraded to the HTC Advantage, not so much for the phone, but more for the 5" screen 8) and it is my primary reader now! Love it!
I find that I like no hands reading- and reading in bed is great!
I've bought close to 1000 books on a couple of sites and have not quite that much with MSReader.
The main pleasure is that I can pick and choose what I want to read, when I'm travelling and even in the early hours of the morning- I can choose, download and start to read.
Baen.com started me on my e-books back in 2001 and I've never gone back. Fictionwise has a great site with lots of rebates and sales and If I can't find it (author or book) to purchase I can always search for it in .lit form. The Kindle looks interesting, but for me- I am really happy with my 5" screen that I don't need to look for anything else.