I tried to download the Nook reader for Android, however I got the message: “the item cannot be installed in your device’s country”. This is for my Bell Samsung GT9000M smartphone.
There’s also a lot of comments on the Marketplace page for the Nook for Android update. There seems to be issues with accounts not being recognized and books not being able to be read.
You may want to hold off updating your smartphone until these problems have been resolved.