Why do you think it's highly cited? 

It deals with a subject that concerns all people on Earth-their origins and remote prehistory.

  Does it describe a new discovery or methodology that's useful to others? 

Yes, a new palaeontological discovery. Usefulness doesn't enter into the matter, as it is more cultural and scientific than technological or financial.

  Could you summarize the significance of your paper in layman's terms? 

Yes. Orrorin tugenensis is a 6 million year old bipedal hominid with several ape-like features of the front teeth, jaw, humerus and finger bone, but with more human-like features of the back teeth, mandibular symphysis, and leg bones. As such Orrorin is by far the earliest known member of the family of man (Hominidae) and is already quite distinct morphologically from the African Great Apes (Gorillidae). This indicates a divergence between Hominidae and Gorillidae that dates back to a substantial period prior to 6 Ma, and we estimate about 8-7 Ma for this event. If so, then the discovery of Orrorin refutes all hypotheses in which humans diverged from apes later than 7 Ma, including most of the recent estimates by molecular biologists who tend to think of the divergence as having taken place later than 5 Ma, and even as recently as 2.5 Ma. In other words, the much vaunted "molecular lock" seems to be telling us the wrong time. 

The fact that Orrorin is found with other fauna that indicates a wooded to forested environment, tends to refute the "savannah" hypothesis of human origins. It seems more likely now that bipedalism originated from an arboreal ancestor, rather than via a knuckle-walking ground dweller similar to chimpanzees. Thus, previous palaeoecological and palaeoenvironmental scenarios of human origins will need to be reconsidered in light of the new data.

Furthermore, in some features of the dentition and femora, Orrorin is more human-like than any of the australopithecines (Lucy and her kin) which raises the possibility that australopithecines are a side branch of hominid evolution that went extinct without issue about 1.5 Ma. If so, then there would have been a more direct line of descent between Orrorin and Homo, via a Pliocene form (possibly Praeanthropus).

Finally, the period 8-7 Ma was one of major faunal change world-wide. In Africa there was a massive change from archaic lineages prior to 8 Ma to more modern lineages after 7 Ma. The characteristic African fauna that we observe today (hippos, rhinos, modern subfamilies of antelopes, monkeys, giraffes, hyaenas, elephants, leopards, porcupines, hares, ostrich, etc) appeared during this transition, whereas many archaic lineages became rare or disappeared altogether. Hominids were part of this change, and thus hominid origins can be better understood as being part of an overall change in African mammal faunas that took place between 8 and 7 Ma. Previous hypotheses of human origins led to the rather unlikely scenario that human evolution was delinked from that of other African mammals. If we are correct, then the origin of the human lineage was part of a generalised faunal shuffle, and as such the forces driving it are more understandable.

The cause of the major faunal change between 8 and 7 Ma was probably the growth of the Artic Ice Sheet to a size where it started to impinge on global climatic patterns, in particular squeezing the northern climatic zones (arctic, taiga, boreal, subtropical) equatorwards. This event led to the borealisation of much of mid-latitude Eurasia with many mammal lineages going extinct in Eurasia, and to the onset of desertic conditions in Africa (Sahara in particular) with an attendant diminution in areas covered in forests. The vegetational changes forced by this climatic change included the installation of large areas of grasslands and woodlands, which in turn led to a large scale change in food resources for African mammals, with many lineages (elephants, pigs, antelopes, rhinos, equids, etc.) developing high crowned cheek teeth and cementum on the teeth. Early hominids initially remained faithful to their largely frugivorous diet (i.e. their teeth did not change much), but they developed a new way of getting between food resources - bipedalism, whereas most mammal lineages merely changed their diet as the vegetation changed around them (and barely altered their locomotor repertoires). This is why the study of locomotion is so important for understanding hominid origins.