The iLiad 2.0 should at least give you 10 hours. Up to 15 if you are just reading.
WiFi works fine as long as you dont need special encryption. It works with WEP and WPA TKIP2.
And it has the largest screen available, and is the only device that can zoom into PDFs so far.
CyBook and Sony are smaller, but their battery lasts much longer. So it mainly depends on your needs
