I guess that depends on how you define it.
A million years ago in digital time (about 2000), I got a Sony Clie (a Palm OS PDA). I tried to use it for a bit of reading, but without much success. Shortly after that, I got an HP iPaq. A wonderful PDA. Read a few books from the Baen Free Library using Microsoft Reader on it. Good, but LCD, so battery life and eye-strain issues. I still have these around someplace, but they're inactive.
Tried to find a decent reader for the Nokia 5230 phone I had a few years ago. Nothing worked well.
My current phone is the Google Galaxy Nexus. I use the Google Play book reader, Aldiko, FB Reader, Moon+ Reader, and Cool Reader apps. I use FB Reader most on my phone. I use it when commuting. I always have the phone with me, so why not?
We also have a Sony T1 that was purchased as an anniversary gift for my wife. I was supposed to get to use it sometimes too, but I never see it anymore.
I did enjoy using it. There is one on its way as a Christmas gift for me. I prefer its features to the T2, based on what I have read.
Honestly, I don't know how one can justify having multiple e-readers. I can understand having a phone, a tablet, an e-reader, and a PC, but not more than one functional, stand-alone e-reader. I just don't have the dough for that.