True, it's pay-for-capacity and that's worse for the user. On the flip side, the constant factor seems to be about 20x cheaper (caveat: this is based on my personal experience with SimpleDB; since Amazon doesn't seem to explain how "box usage" is computed, I don't know how broadly applicable my experience is).
The big plus for Capacity Units is that Amazon actually provides a deterministic model for figuring out what you'll be charged for a given query.
The big plus for Capacity Units is that Amazon actually provides a deterministic model for figuring out what you'll be charged for a given query.