I saw a guy on the train the other day reading a first-generation Kindle. It was kind of sweet.
I am starting to see lots of ebook readers in the wild--mostly Kindles, but there are a few Sony Readers in the mix. I have yet to see a nook, which surprises me. Also there are lots of people on the train every day petting iPhones and other smartphones, and it stands to reason that some of them at least are reading ebooks.