disadvantages of natal::
-will be expensive
-will have expensive development costs, the code written for natal will be quite different than button-controlled games
-natal games wont bring in nearly as much, if PSN games are any indication, the offerings by natal wont be that AWESOME as they will mostly be downloads
-MS doesn't have a casual userbase
-lag
-limit of kinds of games that would be ideal for natal, like say a yoga game or something