Wow... I am an amateur compared to some of these folks. Still new to the field (as of springtime)!
Kobo Mini: My first e-reader! Bought on a whim in April. Love it; it does what I need it to, and is definitely my go-to device. Just bought one on sale to give to my mother for a birthday gift.
Sony PRS-350: Hubby's eReader. We originally bought the Mini and the PRS-350 at the same time, intending to try them both and keep the one that we liked the best, but each of us liked different ones for different reasons (preferences) and we realized we wouldn't be able to SHARE one reader...
Sony PRS-650: I bought this last month to try a larger screen and the Sony format (love the Mahjong on the hacked firmware!)... but I don't use this as much as my Mini.
HP Touchpad, iPad, iPhone 4S: Not a fan of reading on LCD screens, so until I got my eInk device I had never used the reading apps on them. I still prefer using them just to read image-intensive eBooks (I like to pick up the freebies on Kindle once in awhile).