This is cool but it's a real crack in the "walled garden"; if anybody can hack the files that "belong" to any app it could be easy to circumvent security, cheat at games, etc.
imo: Microsoft could have put more effort in this topic to make it a little bit safer
(and, y'know, you could pay for stuff that you like using, feed a developer's starving family and continue to get updates and improvements rather than ripping them off)