I've bought a Nook, and I'm using it for reading on long journeys, but I'm being careful not to let it displace my book-buying habits, precisely because I want to be one of those people with a houseful of awesome books when I get older.

Therefore, my rule is this: I only use the Nook to read things which are public domain. There's more than enough public domain stuff I want to read out there to keep me occupied. But if I'm going to pay for something, it's gonna be a proper printed physical book which I can keep for the rest of my life.