Convenience
This is a great service that shows that Soda Sense saw a need and filled it. The net cost per bottle is $5 more than the other guys, but the other guys obviously dropped the ball by losing. stores willing to carry their refills.
This program is extremely convenient - I don't have drive all over town to find a store that still carries the refills. I just pop the empties in the mail and a few days later I have the refills. Nice. I no longer have a cupboard with 4-5 empties in it!
The only question is whether the life of the soda sense canisters are are "full" as the others. I think I'm getting 2-3 fewer bottles per canister. Too soon to tell. But the convenience and ease makes all the difference.