Haven't looked at the API in question yet.. but after reading the above and the other one about Amazon potentially proving REST unnecessary I think, in the interests of fairness, it's worth clarifying a couple of aspects of REST which seem to be being overlooked.
First off - "doing REST" or "being RESTful" doesn't have much concern with achieving short-run simplicity or making life easier for your clients, that is a miss-conception. In fact, creating a RESTful application for machines (i.e. an "API") is, at this point in time, probably more challenging for both client and server; as there are still some relatively unknown quantities and considerations - specifically in media type design and/or selection. For example; there is no HTML of the machine web. Yet.
Second - What is an explicit objective of RESTful design (particularly hypermedia) is the long-term evolvability of your application/system. This REST stuff isn't esoteric or religious, it is solid theory based on high quality analysis of the most robust distributed system ever produced by a bunch of talking monkeys. If in doubt you could always read the dissertation where the term came from.
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RESTafari prophecy holds that the less RESTful applications will struggle to manage change and avoid breaking tightly coupled clients. This will negatively impact the speed and cost of innovation - making them less competitive over time.
In the end, longer-term case studies will do a much better job of illuminating whether or not REST actually delivers on the (business) value it promises, and whether the "simpler" solutions for the short-term continue to be sustainable and cost effective in the long run. Until then, you're probably jumping the gun a bit.
Designing, building and cultivating a system that efficiently evolves over time could present a significant long-term competitive advantage for API providers that get it right. I think that's worth some consideration.
I'll finish with a quote from the great Bob Marley:
"Facts an' facts, an' t'ings an t'ings: dem's all a lotta fockin' bullshit. Hear me! Dere is no truth but de one truth, an' that is the truth of Jah Restafari."
Cheers,
Mike