I've used the previous 3 x 7 system on a recumbent, but haven't used the Dual drive. I don't think it compares to a Rohloff since it has many of the problems of a derailleur drivetrain plus the losses due to the planetary gears in the IGH. However, it seems to work well enough that if the cost is considerably less than it would merit attention...I don't know what they cost. If the cost starts approaching Rohloff territory I would stick with a Rohloff. If you can get the DD for 30% of the cost of a Rohloff its probably worth it.

The Rohloff will still be working after 100,000kms...probably after 200,000kms so the operating cost is low if you ride enough kms.

If the Shimano Alfine 11 turns out to be a good IGH I think I would use it instead of the DD or Rohloff since it provides most of the benefits at less than 50% of the cost.