I agree that a tablet's software library is a key factor in a tablet's success, but I lump it in with operating system choice: iOS = App Store, Android = Market, Windows Phone = Marketplace, WebOS = well....
As for the foil, there are other (more repair-friendly) ways to shield components. For example, check the following cracking open galleries of tablets without massive amounts of foil shielding:
Acer Iconia Tab
http://www.techrepublic.com/photos/cracking-open-the-acer-iconia-tab-a500/6279615Asus Eee Pad Transformer
http://www.techrepublic.com/photos/cracking-open-the-asus-eee-pad-transformer-tf101/6270147Toshiba Thrive
http://www.techrepublic.com/photos/cracking-open-the-toshiba-thrive/6260686