As I said in another thread, although it was somewhat off-topic there, each of my e-readers has a niche to fill - think of Darwin's finches...
iPaq PDA: used to be my main e-reader (and calendar/e-mail/etc.), demoted since I got my Android phone, getting VERY long in the tooth now so I use it as my gym/exercise bike reader, and I don't worry about it getting sweat on it - if it dies, so what!
Android phone: most of my reading since I carry it everywhere already, backlit and small so I can read it it bed easily (backlit screens don't bother me)
PRS-300: e-ink, read in sunny places, long battery life - so good on trips
Nook Color: rooted - use to read .pdf's that don't fit well on smaller devices, use as a tablet to take notes, and sometimes to read normal stuff when I'm carrying it anyway
Kindle keyboard SO: new, only had it a few days (how could I pass up $89 at Best Buy last weekend) - e-ink and long battery life so it fills the same niche as the PRS-300; thinking about "demoting" one of the two to replace the PDA as the gym/exercise bike reader; also I was curious about the SO, some of which have sounded pretty good
BTW, I CAN resist e-readers
- I really really wanted also to try the Nook Simple Touch that was on sale at BN on Black Friday, but couldn't figure out any justification to buy it AND the Kindle