We gave a Kobo Vox to both of our girls this year (both age 7). They voraciously tore through the books that were on them (including the free dessert cookbook), and are looking for more. Magic Tree House e-books, here we come!
I installed an app locker on the Voxes (Voxi???) , and locked out the WiFi and other apps I felt were not appropriate (ie Facebook, YouTube etc). However, I did install Angry Birds and Cut the Rope in my bid to win the "Coolest Dad Ever" award