Since I still have unread pbooks, I tend (like someone else said earlier on) to try to find a pbook after 3-4 ebooks. I still like pbooks just fine, but the main thing I notice when I'm reading one is that I sometimes start searching for the 5-way button to do a dictionary lookup.
For me, that's the gift that just keeps on giving, day in and day out. I adore that built-in OED on my Kindle. If it was the full OED, I'd marry the thing.
