I found on my Kindle 2 that during direct noon-day sunlight in 100 degree+ temperature there was an ink fading issue between screen refreshes. I also found that when I went to a different font that the fading issue was minimized to nearly non-existent. For me this is a small extreme use issue and I don't normally read in full direct sunlight (I prefer a slightly shaded area). Also worth mentioning I didn't have this issue during more temperate times of the day.
On the topic of LCD vs. E-Ink. I used to read on my Jornada 525 PDA, but could never even think of reading outside even in the shade as the LCD screen was too poor to show in sunlight.
Honestly though I am looking forward to seeing some of the new technology from
http://www.pixelqi.com/ if they can produce a LCD screen that has color, is easy to see in sunlight and has reasonable battery consumption that would be my silver bullet screen type.