I have met people who have identified as transgenderist. It is more of a philosophy and many people who identify as such are non-op transsexuals, though there are some which are post op TS. It is not a clinical term, but there are people who identify as such.
The best example of transgenderist is Kate Borenstein (Gender Outlaw, My Gender Workbook, etc).
I will say if you meet a transgenderist, they are more likely to be younger and in an urban/college environment. I would say the term is more common for those under the age of 30. I came across the term all the time in the Chicago area. It is basically a particular philosophical idea of being beyond gender...transgressively gendered. Honestly...look into Kate Borenstein's books.
The terms themselves save for the clinical ones can be location specific. For example...genderqueer, not really used that much in Chicago, but used frequently in DC/Baltimore/Boston.