Use this instead: A blender
Unless you regularly host bitchin' pool parties with hordes of frozen-beverage enthusiasts, there is little to no need to invest in what is basically just a tropically themed blender with insecurity issues. A margarita maker is the appliance equivalent of the guy who goes to Señor Frog's for the appetizer specials.
But guess what? Virtually every blender has a "Crush Ice" button. So instead of buying a massive, expensive kitchen appliance, get a multi-purpose blender, like an Oster Reverse Crush counterforms blender, or, if you want to splurge, a Vitamix (which, admittedly, is more expensive than a margarita maker, but is damn more useful). It even has a "Frozen Drinks" button. Just add the ice right alongside your margarita ingredients and blend away.