Watch out if you're looking to read mostly PDFs. I'm in your position, and I found the Nook to be a beautiful device that was completely unsuitable; since the device can't reflow or scale fonts on PDFs, the screen just turned out to be too small to read all the PDFs I tried it with (even after manually trimming off all the margins and page numbers.)

I'm considering buying a Kindle DX, which I believe would be ideal, but it's hard for me to justify that when Pixel Qi hybrid tablets may be coming out in the next year.