I now am the proud owner of two different platforms of single-serve coffee machine, the Tassimo and the Nescafe Dolce Gusto. Each machine seems to have its "core competency": the Dolce Gusto is the master of hot chocolate (it's Nestle, natch); the original, IMHO superior Braun Tassimo machine does drip coffee really well, and the newer Bosch Tassimo is best at espresso drinks with milk. If any machine on the market seems superfluous to me, it's the victorious Keurig platform--the VHS of single-serve coffee.
What's the attraction? That depends, in part, on how much quality coffeehouses manage to deliver. I'd argue that Starbucks has somewhat more to lose than to gain, but not much more. For one thing, single-serve coffee "trains" the consumer to perceive that a cup of brewed coffee should cost a dollar. That's not quite what SBUX charges in its cafes, but it's better (in their eyes) than having the customer perceive that a cup of brewed drip should cost ten cents--its approximate cost when brewed by the pot. The business end of that wedge, however, is the perception that a passable espresso drink should cost less than a buck. For that is precisely what the Tassimo delivers.