While a .POST domain for postal-related entities has as much logic behind it as other limited-special-interest TLDs like .MUSEUM and .AERO, I have strong doubts that it would get much actual use (as, for that matter, .MUSEUM and .AERO have not been much used). Postal entities such as the United States Postal Service have shown little inclination to use the proper TLD even in the current system; the USPS disdained their proper original address, USPS.GOV (given that they are a U.S. government entity) and insists on "branding" their site inappropriately as USPS.COM. Apparently, even governmental entities can become infested with Marketing Types.
Thus, while I've got no problem with .POST being approved as a sponsored domain, I doubt that it will end up getting any productive use. I'd love to be proven wrong, however.
-- == Dan == Dan's Mail Format Site: http://mailformat.dan.info/ Dan's Web Tips: http://webtips.dan.info/ Dan's Domain Site: http://domains.dan.info/