I'm generally against all in one devices particularly if I heavily use a specific function. But I would use a smart phone since I dislike Verizon's dumb ones. I even have a Canon multifunction printer but I don't heavily scan or print so it makes sense to combine those functions.
<An aside> My Canon multifunction printer died yesterday, I called tech support and after going through a few hoops a replacement was sent. Received that replacement this morning and sent the broken back. That's excellent service.
Back on topic...
My personal preference is to have a dedicated reading device *until* such time as the tech improves to give me color eInk or similar tech with long battery life and low weight.