There's a large gulf in battery life between phones and laptops - there are plenty of times where I'd like to browse something on my laptop, but I don't feel like getting the charger from the other room and plugging in. So a device that gets 8-12hrs battery life under use would have a different use profile.

There are also apps like instant messengers, skype, email etc. that you'd like to be always-on. The iPhone is a one-app-at-a-time, goes-to-sleep often device that's not well suited to those applications.

Slapping in a user-facing camera for video calls would also differentiate it from the iPhone.