As many others have stated, space was one issue... I also had a lot of technical books as PDF's that I couldn't manage to sit in front of a computer screen long enough to read, so I wanted something more portable.
I tried several devices including a Handspring Treo 90 and the Franklin eBookMan until I found the RCA REB1100 (RocketBook) which was backlit and allowed me to carry around multiple books (especially after I added a 128MB SmartMedia card).
I can't even remember where I got it, but probably some electronic surplus place. Again, as others have mentioned, I discovered FictionWise and Baen and began consuming fiction on it. It still didn't address my PDF needs, and the conversion tools were not that helpful. I was happy with the REB1100 and especially loved the built in dictionary, but I still needed a way to read PDF's...
While traveling, I saw an early Sony eInk device (probably the 500 or the 505) at Borders... I'd heard of them, but couldn't afford the high prices they wanted. I'd also gotten used to touch screens from the Treo 90, Axim X5, REB1100, and other devices... I eventually ran across a refurb Sony PRS600 on Woot... touchscreen, but not backlit... I bit the bullet and while it was a shift going from the REB1100 to the PRS600, I fell in love with it. It could actually do PDF, but it was a bit of a pain, so I was a LITTLE closer to THAT goal anyway...
I eyed the Kindles when they came out, but I liked the touchscreen and the more minimalist design of the Sony... I thought the keyboard made it too chunky and ugly...
I also looked at the nook and disliked it for the same reasons as the Kindle.
I know the 600 had a bit of an issue with glare due to the touchscreen as well as some of the screens fading in direct sunlight, but those issues didn't bother me enough to make me upgrade to the 650, although when I saw a deal on the T1, I decided to upgrade...
I now have a couple of tablets to handle my PDF's, so I'm good on that score as well, although I use my T1 for most reading.