We've had a Sodastream for over 10 years, but this seems to be much more expensive than that. One of the reasons we bought Sodastream was for environmental reasons. Of course drinking tap water is the most green thing one can do, but my husband likes diet soda, and this way, we used reusable bottles and fossil fuels weren't used to haul the actual soda around - just the bottles of syrup. It ended up being cheaper than Diet Coke or Pepsi, although I swear my husband drank more this way, since it came in 1 liters instead of individual cans.
And the price can't be beat for seltzer with the Sodastream.
When I first read this, I was grossed out, because I thought it was the same machine as the coffee pod thingie. That would be disgusting, since all your soda would taste like coffee. The few times I've been a someone's house with one of this dumb contraptions, I've found you can't brew anything in a Keurig except coffee. Tea always ends up tasting like coffee, as does hot chocolate.