I read for years on PDAs but was never satisfied because I found reading on the small backlit LCD tiring. YMMV. Since I purchased my first Kindle I've read more with far less eye fatigue. It's not just the difference between eInk and LCD. The screen size is far larger on the smaller Kindles and I find it less tiring to track on a larger screen.
I do like my Droid but only read on it when I'm away from home. I used to carry my Kindle but the reading experience on the Droid is good enough for short reading sessions. A big plus for me is the ability to sync between my Kindle and my Droid so I don't have to remember where I stopped reading on each device.